Patent Grant
11195683
Embodiments of the present disclosure relate to single bolt fuses and, more particularly, to a novel way to attach the single bolt fuse to a female battery or power cable.
Fuses are current-sensitive devices designed to serve as the intentional weak link in an electronic circuit. Fuses provide protection of discrete components or of complete circuits by reliably melting under current overload conditions. Fuses come in a variety of packages and ratings to suit to their intended application.
Single bolt fuses, also known as battery terminal fuses, are a particular type of fuse package in which the fuse is attached to a device or circuitry by a threaded connection, such as a bolt or stud. The fuse includes a hole through which a single bolt may be inserted to mechanically connect the fuse to the device or circuit. The bolts are specially adapted, such as by being insulated or otherwise materially treated, so that they do not disrupt or become part of a current path through the fuses, ensuring that the single bolt fuses operate as designed.
To use the single bolt fuses, the specially treated bolt is separated from the fuse, the fuse is attached to the circuit or device to be protected, the bolt is inserted through the hole in the fuse. Sometimes, the bolt has an integrated nut, or bolt may be secured by a separate nut. Because of the assembly needed with single bolt fuses, the bolt (and nut, if present) may become separated from the fuse and lost. Customers may be tempted to replace the lost bolt with a standard bolt that is not specially adapted for the single bolt fuse. Unfortunately, this results in the single bolt fuse not functioning as designed. Further, the single bolt fuse is designed to be connected between a power terminal and either a battery terminal or a bus bar, which somewhat limits the applications in which the fuse may be used.
It is with respect to these and other considerations that the present improvements may be useful.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.
An exemplary embodiment of a fuse assembly in accordance with the present disclosure may include an insulated steel bolt and a metal terminal. The insulated steel bolt includes a shaft that is part threaded and part insulated. Connected to the shaft, the insulated steel bolt also includes a base, which is a rectangular cube having a first dimension. The shaft is positioned vertically atop one side of the base. The metal terminal features a bolt base receptacle, also shaped like a rectangular cube, and having a hollow interior with a second dimension that is greater than that of the base. The base of the steel bolt fits into the hollow interior of the bolt base receptacle. The metal terminal also has a threaded shaft on one side of the bolt base receptacle. The shaft of the insulated steel bolt is to be fed through a cylindrical opening of a fuse.
Another exemplary embodiment of a fuse assembly in accordance with the present disclosure may include an electrically conductive landing pad which has a threaded shaft and a hollow receptacle. The threaded shaft fits into a receiving aperture of an electrical device. The fuse assembly also features a stud that has an insulated base portion, an insulated washer, and a shaft. The shaft has a threaded portion, an unthreaded portion, and an insulated portion. The base portion of the stud fits into the hollow receptacle of the landing pad and the shaft portion fits through a cylindrical opening of a single bolt fuse. In the fuse assembly, current passes from the electrical device, through the single bolt fuse, and to a second electrical device without passing through the stud.
A single bolt fuse assembly and method to connect a single bolt fuse to a circuit or device are disclosed. The single bolt fuse assembly enables the single bolt fuse to be used on any electrical device having a hole suitable for receiving a threaded shaft and connectable to a circuit or device that electrically connects to a female battery or power cable. The apparatus includes a separate high-conductive metal terminal that mates with the stud that mechanically attaches the fuse between the electrical devices. The stud is insulated, thus isolating the bolt from becoming part of the electrical circuit and ensuring proper operation of the fuse. By mechanically attaching the stud to the metal terminal, the stud is unlikely to get separated from the fuse. The metal terminal and stud may be part of a kit available to customers who purchase the single bolt fuse.
Thus, the fuses 100, 200, and 300 are designed to be used with their respective studs 110, 210, and 310. The studs are insulated to isolate current so that the current passes through the fuse (and not the stud), enabling the fuse to protect the circuit (e.g., the circuit or device connected to the output cable 212 (
One problem with single bolt fuses, including the above illustrated single bolt fuses, is that the studs that are specially made to be used with the fuses may become separated from the fuses. Customers may then be tempted to replace the missing studs with standard bolts that are uninsulated. When this occurs, the fuse will not operate as designed.
For example, in the assembly of
If, in the alternative, the insulated stud 210 is replaced with an uninsulated stud not designed to be used with the fuse 200, current will flow from the battery 204, through the uninsulated stud, and through the sealed cable 212, completely bypassing the fuse 200. The same will happen in the other direction: current will flow from the circuitry to be protected (not shown) through the sealed cable 212, through the uninsulated stud, and to the battery 204, completely bypassing the fuse 200. Put another way, the uninsulated stud will electrically connect the top and the bottom of the fuse, removing the fuse from the circuit. Thus, the use of a stud not designed to be used with the fuse 200 will prevent the fuse from operating as designed to protect the circuitry. Similar problems will exist for the fuses 100 and 300 if they are used with uninsulated studs.
Another problem with single bolt fuses is the limited environment in which they can operate. As currently designed, the fuses are connected, at one end, to the battery or power cable and, at the other end, to either a battery terminal or to a bus bar. In the example of
An alternative is provided in the apparatus of
The metal terminal 402, also known as the “landing pad” of the fuse assembly 400, includes a bolt base receptacle 404 and a threaded shaft 406. The threaded shaft 406 enables connection of the single bolt fuse assembly 400 with any electrical device having a threaded receiving aperture. The metal terminal 402 further includes an adjacent side opening 424, revealing a hollow interior, as well as an inset portion 414. In exemplary embodiments, the threaded shaft 406 and the bolt base receptacle 404 of the metal terminal 402, including the opening 424 and the inset portion 414, are machined from a unitary metal piece made of electrically conductive material, such as copper or a copper alloy.
The steel bolt or stud 408 of the single bolt fuse assembly 400 features a shaft 410 that has a threaded portion 412, an unthreaded portion 416, an insulated portion 418, an optional integrated washer 420, and a base 422. In addition to the insulated portion 418 of the shaft 408 being insulated, the integrated washer 420 and the base 422 are also insulated so as to isolate them from current transmitted through the assembly. In addition to providing insulation so as to prevent current flow through the stud 408, the integrated washer 420 also helps to withstand pressure after the assembly 400 is secured by the nut 440. In an alternative embodiment, the insulation of the base 422 is sufficient to prevent current flow through the stud and to withstand high mechanical pressures during torque of the nut 440. Thus, the stud 408 may be configured without the integrated washer 420. In an exemplary embodiment, the insulated components of the assembly 400 are insulated using electrically insulating material, such as overmolded plastic, though other insulation materials may also be used.
In the illustrations, the bolt base receptacle 404 is a rectangular cube shape of a first dimension. The hollow interior of the bolt base receptacle 404, which is a second dimension smaller than the first dimension, is disposed on one side adjacent the side with the threaded shaft 406. As illustrated in
Alternatively, the two shafts 406 and 410 may be in different axes. For example, where the bolt base receptacle 404 is now substantially cubic in shape, a more elongated rectangular cube-shaped receptacle may result in the shaft 406 of the metal terminal 402 being in one axis and the shaft 410 of the stud 408 being in a different axis, with the two axes being parallel to one another. Or the inset portion 414 may be machined into a different side of the bolt base receptacle 404 (a side not opposite the threaded shaft 406). This would result in the shaft 410 of the stud being in an axis orthogonal to the threaded shaft 406. Or the opening 424, which is now on a side adjacent to the threaded shaft 406, may instead be on the side opposite the threaded shaft, where the inset portion 414 is now located, in which case the shaft 410 of the stud would be orthogonal to the shaft 406 of the metal terminal 402. Designers of ordinary skill in the art will recognize a number of ways in which the landing pad 402 may be machined to receive the base 422 and shaft 410 of the stud 408 without departing from the spirit of this disclosure.
Once inserted into the landing pad 402, the insulated steel bolt 408 may be captured or mechanically locked in the bolt base receptacle 404. In an exemplary embodiment, orbital riveting, a mechanical bottleneck, a secondary lock, or other means are employed to mechanically lock the bolt 408 to the metal terminal 402.
The fuse 426 of the single bolt fuse assembly 400 includes a cylindrical opening 428, a shaft receptacle, for receiving the shaft 410 of the stud 408. In an exemplary embodiment, once the insertion of the shaft 410 through the fuse is complete, the single bolt fuse 426 is disposed atop and adjacent to a top surface of the bolt base receptacle 404, as illustrated in the cutaway view of
Similar to other fuses, the single bolt fuse 426 includes within its housing a fusing element (the intentional weak link that breaks upon the occurrence of an overload event, such as overcurrent, overvoltage, or both), connection means for connecting the fusing element to terminals (ensuring that the fusing element is part of a closed circuit), and fusing powder. This part of the fuse 426 containing the fuse element is known herein as the fuse element housing. In an exemplary embodiment, the shaft receptacle 428 is isolated from the fusing element housing. The fusing element housing of the single bolt fuse 426 may thus be thought of as an annular housing, shaped like a rectangular donut, with the shaft receptacle 428 being both physically and electrically isolated from the fusing element housing.
Atop the fuse 426, the single bolt fuse assembly 400 includes the female battery or power cable 430, which includes a cable 432 and a high-current electrical (ring) terminal 436. The cable 432 attaches the fuse 426 at one end to a circuit or device to be protected (not shown) while the threaded shaft 406 of the landing pad 402 attaches the fuse at the other end to virtually any electrical component that has a hole through which the landing pad may be threaded, enabling the electrical component to be electrically connected to the fuse 426. The threaded portion 412 of the stud 408 is fed through the ring terminal 436, and the female battery or power cable 430 is attached to the assembly by an optional washer 438 and a nut 440. In the illustrations, the nut 440 is a flange nut, but a regular nut may also be used as long as torque loosening is avoided during use of the assembly 400. In the single bolt fuse assembly 400, the washer and the nut are not part of the current path, and so need not be insulated. This means that, if lost, the optional washer and nut may be replaced without compromising the operation of the fuse 426.
The low-resistant landing pad 402 lets current flow through the fuse 426 and the battery or power cable 430. The steel insulated bolt 408 guarantees a high torque to fix the assembly 400 without being involved in the electrical flow.
Single bolt fuses, such as the prior art single bolt fuses described and illustrated above, feature M6, M8, and M10 sized threaded holes for connecting with M6, M8, and M10 insulated studs, respectively. However, the single bolt fuse assembly 400 may be designed with a threaded shaft of any size, sized to fit with a single bolt fuse having a hole of a similar size. The examples herein are not limited in regard to the size of the threaded shaft or the threaded hole.
The shaft (410) is next inserted through the receiving aperture or shaft receptacle (428) of the single bolt fuse (426) until the fuse is disposed atop the bolt base receptacle (404) of the landing pad (402) (block 706). At this stage, the insulated portion (418) of the shaft (410) is partially inserted into the receptacle (428). The ring terminal (436) of the female battery or power cable (430) is positioned over the shaft (410) of the stud (408) until the ring terminal (436) is flush against the top surface of the single bolt fuse (426) (block 708). Finally, the washer (438)), if present, and nut (440 are disposed over the shaft (410) of the stud (408), and secured tightly thereon (block 710). Alternatively, the shaft (410) of the stud (408) is secured by a nut having an integrated washer, such as a flange nut, a trilobate nut, or other type of nut that can be used without a washer.
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.
While the present disclosure makes reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claim(s). Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.
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