Fuses are widely used as over-current protection devices for preventing damage to electrical circuits. Fuses include fuse terminations configured to form an electrical connection between an electrical power source and an electrical component or a combination of electrical components or loads arranged in an electrical circuit. Fuses also include one or more fusible links or elements disposed between the fuse terminations. When electrical current through a fuse exceeds a predetermined limit, the fusible elements melt, disintegrate, fail, or otherwise open to break an electrical and open the electrical circuit associated with the fuse, thereby preventing damage to the electrical components in the circuit.
In vehicle electrical systems, storage batteries or power sources such as alternators are used to power electrical circuits. Typically, a storage battery includes a terminal post configured to receive a ring terminal of an electrical cable in an electrical circuit. Sometimes, a fuse is fitted over the terminal post to protect the components of that electrical circuit from excess current. Alternatively, the fuse is sometimes fitted over a mounting stud of a mounting plate coupled to the terminal post. A nut is fitted over the terminal post or mounting stud to maintain the positions of the ring terminal and fuse relative to the terminal post or mounting stud.
Known arrangements of these types may be susceptible to undesirable shorting or bypassing of the current path through the fuse if the ring terminal is inadvertently brought into contact with the terminal post or mounting stud, creating a direct current path from the terminal post or mounting stud to the ring terminal, without first passing through the fuse. Thus, despite the presence of the fuse in the circuit, component damage may result.
Traditionally, an insulating nut has been fitted over the terminal post or mounting stud to electrically isolate the fuse and the ring terminal and thereby prevent current from circumventing the fuse. A consumer who is unaware of, or unconcerned with, this important function of the insulating nut may replace the insulating nut with a less expensive, standard nut. The standard nut will not prevent current from circumventing the fuse and thereby causing component damage.
FIG. 1 is a perspective view of a conventional fuse 10 for storage batteries. The fuse 10 includes a cubical-shaped member 15 having a fusible element 20 therein. The term “cubical” is used herein to refer to any 3-dimensional member with rectangular sides. The fusible element 20 includes a fault element 20a configured to melt, disintegrate, fail, or otherwise open to break an electrical circuit (not shown) coupled to the fuse, in response to an over-current in the circuit. A transparent cover 25 is coupled to the cubical-shaped member 15, on a side of the cubical-shaped member 15 proximate to the fault element 20a. The transparent cover 25 allows for visual inspection of the fault element 20a. 
An aperture 30 is disposed between the fault element 20a and the cover 25. Ambient air and other particles (hereinafter, “ambient particles”) may travel through the aperture 30 and deposit on the fault element 20a. Such deposits can significantly degrade the performance of the fault element 20a. The degradation is especially prevalent in marine applications, where the ambient particles include water particles, minerals, etc. For example, the water and mineral particles can cause the fault element 20a to rust. The aperture 30 also prevents the fuse 10 from being ignition protected, as a spark from the fault element 20a, such as an electric arc caused by an over-current, can ignite a fuel/air mixture in the ambient particles.
Therefore, a need exists in the art for a battery fuse assembly with an improved means for preventing electrical circumvention of the fuse. Another need exists in the art for the fault element of the fuse to be protected from degradation by the ambient particles. A further need exists in the art for the fuse to be ignition protected.