Patent Application
20180061607
Embodiments of the present disclosure relate generally to the field of fuses, and more particularly to a fuse and method of forming a fuse.
Fuses are used as circuit protection devices and form an electrical connection with a component in a circuit to be protected. One type of fuse includes a fusible element disposed within a hollow fuse body. Upon the occurrence of a specified fault condition, such as an overcurrent condition, the fusible element melts or otherwise opens to interrupt the circuit path and isolate the protected electrical components or circuit from potential damage. Such fuses may be characterized by the amount of time required to respond to an overcurrent condition. In particular, fuses that comprise different fusible elements can accommodate varying amounts of current through the fusible element. Thus, by varying the size and type of fusible element, different operating times may be achieved.
When an overcurrent condition occurs, an arc may be formed between the melted portions of the fusible element. If not extinguished, this arc may further damage the circuit to be protected by allowing unwanted current to flow to circuit components. Thus, it is desirable to manufacture fuses which extinguish this arc as quickly as possible. In addition, as fuses decrease in size to accommodate ever smaller electrical circuits, there is a need to reduce manufacturing costs of these fuses.
Existing fuses include a blind assembly of the electrical connection between the fusible element and an end cap. A solder plug is disposed on an underside of an end cap, and the fuse is heated so the solder reflows. Ideally, the solder reflows and electrically connects the fusible element with the end cap, so that each end of the fuse is electrically connected. However, it can be difficult or costly to thoroughly inspect the solder connection without destructive testing. Undetected defects in the solder connection may result in decreased performance or reliability of the finished fuse.
A need therefore exists for a fuse that can be easily inspected during the manufacturing process to ensure high quality control.
An embodiment of the present invention includes a fuse comprising a fuse body having a first end and a second end, and defining a cavity. A fuse element is disposed within the cavity, a first end of the fuse element extending beyond a first edge of the first end of the fuse body. A first arc disc is disposed on the first edge of the fuse body, the first arc disc including a notch cut providing a pass-through area for the first end of the fuse element extending beyond the first edge of the first end of the fuse body. The first end of the fuse element is configured to be folded over an outer surface of the first arc disc. A first end cap is disposed over the first end of the fuse body and the first arc disc, the first end cap having a hole at a top surface and positioned to expose the first arc disc and the first end of the fuse element, such that solder deposited within the hole provides an electrical connection between the first arc disc, the fuse element, and the first end cap.
An embodiment of the present invention includes a fuse comprising a hollow fuse tube and a fuse element disposed within the hollow fuse tube, ends of the fuse element extending beyond edges of ends of the hollow fuse tube. Plugs are disposed within the ends of the hollow fuse tube, wherein the plugs secure the fuse element at each end within the hollow fuse tube. Arc discs are disposed on the edges of the hollow fuse tube and covering the plugs, the arc discs having a notch cut providing a pass-through area for the ends of the fuse element extending beyond the edges of the hollow fuse tube, wherein the ends of the fuse element are configured to be folded across an outer surface of the respective arc disc. End caps cover the respective ends of the hollow fuse tube, plugs, arc discs, and folded ends of the fuse element, and the end caps have a hole in a top surface such that the arc disc and folded end of the fuse element are exposed. Solder is deposited within the hole of the end caps such that the respective end caps, arc discs, and folded end of the fuse element are electrically connected.
An embodiment of the present invention includes method for forming a fuse comprising inserting a fuse element in a cavity of a fuse body, ends of the fuse element extending beyond edges of the respective ends of the fuse body. Arc discs are assembled on the edges of the fuse body, the arc discs having a notch cut providing a pass-through area for the ends of the fuse element extending beyond the edges of the fuse body. The ends of the fuse element are formed over an outer surface of an arc disc. End caps are attached over the ends of the fuse body, the end caps having a hole at a top surface of the end cap, the hole being positioned to expose the arc disc and the formed end of the fuse element when attached. Solder is deposited in the hole of the end cap, such that the end cap, the arc disc, and the formed end of the fuse element at each end of the fuse body are electrically connected.
By way of example, specific embodiments of the disclosed device will now be described, with reference to the accompanying drawings, in which:
A fuse assembly in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain exemplary embodiments of the fuse are presented. The fuse may be embodied in many different forms and is not to be construed as being limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the fuse to those skilled in the art. In the drawings, like numbers refer to like elements throughout unless otherwise noted.
A fuse element 120 having terminal ends 120a, 120b (not shown), extend out of the ends 110a, 110b of the fuse body 105. The terminal ends 120a, 120b of the fuse element 120 are bent over the fuse body 105, for example, folded over an edge 135 of the hollow tube and being exposed on an outer surface of the fuse body 105. The fuse element 120 may be positioned diagonally in the fuse body 105, so that terminal ends 120a, 120b extend to opposite sides of the fuse body 105 at the respective ends 110a, 110b. In another embodiment, the fuse element 120 may be positioned in the center of the fuse body 105.
Plug 125 is disposed in the cavity 115 at each of the ends 110a, 110b to secure the fuse element 120 in place. The plug 125 may be flush with the end 110a, 110b of the fuse body 105 when it is inserted into the cavity 115, so that the plug 125 is not extending beyond an edge 135 of the fuse body 105. The plug 125 maintains a desired longitudinal tension with the fuse element 120 by pressing the terminal ends 120a, 120b against the housing wall of the fuse body 105. The plug 125 may be formed of elastic material, e.g., silicone, so that it secures against the inner surface of the fuse body 105 and the terminal end 120a, 120b of the fuse element 120 and holds the fuse element 120 in place. The plug 125 provides arc-quenching properties for the fuse 100, in that the plug 125 seals the fuse body 105 and quenches the arc before the arc reaches the end caps 130a, 130b, preventing a blow-out, or explosion, of the fuse, in an electrical overcurrent event.
End caps 130a, 130b are secured to the ends 110a, 110b of the fuse body 105. For example, end caps 130a, 130b may be secured via ridges 140 on the fuse body 105. The end caps 130a, 130b may be configured to enclose the fuse body 105, plug 125, and end of the fuse element 120a, 120b when coupled to the fuse body 105. Solder preform (not shown) may be disposed on the underside of the end cap, so that when the end caps 130a, 130b are assembled to the ends 120a, 120b of the fuse element 120, the solder preform is adjacent to ends 120a, 120b of the fuse element, the plug 125, and end 110a, 110b of the fuse body 105. During the assembly process, the fuse may become heated, allowing the solder to reflow and form a connection between the end caps 130a, 130b and fuse element 120. This results in an electrical path from end cap 130a to end cap 130b, or vice versa.
As described above, existing fuses where soldering occurs in a blind area presents several challenges. It can be difficult or costly to thoroughly inspect the solder connection without destructive testing. Undetected defects in the solder connection may result in decreased performance or reliability of the finished fuse.
A fuse according to an embodiment of the present disclosure is depicted in
Fuse element 220 having terminal ends 220a and 220b is disposed in the cavity 215, and the ends 220a, 220b extend beyond the fuse body 205. The fuse element 220 may be positioned diagonally in the fuse body 205, so that terminal ends 220a, 220b extend to opposite sides of the fuse body 205 at the respective ends 210a, 210b of the fuse body 205. In another embodiment, the fuse element 220 may be positioned in the center of the fuse body 205. The fuse element 220 is configured to create an open circuit in an overcurrent event. The fuse element 220 may be any known configuration for providing a circuit interrupt, including but not limited to a wire, a metal link, and an element shaped into multiple bends and/or curves.
The remaining open volume inside the cavity 215 may be filled with an arc-quenching material, such as silica sand. Plug 225 is disposed in the cavity 215 at each of the ends 210a, 210b to secure the fuse element 220 in place. The plug 225 may be flush with the end 210a, 210b of the fuse body 205 when it is inserted into the cavity 215, so that the plug 225 is not extending beyond edges 235 of the fuse body 205. For example, the arc disc 245 may be placed on the edge 235 of the fuse body 205. Edges 235 of the fuse body 205 may be the outermost ends of the hollow tube, at each end 210a, 210b. The plug 225 maintains a desired longitudinal tension with the fuse element 220 by pressing the ends 220a, 220b against the housing wall of the fuse body 205. The plug 225 may be formed of elastic material, e.g., silicone, so that it secures against the inner surface of the fuse body 205 and the end 220a, 220b of the fuse element 220 and holds the fuse element 220 in place. Alternatively, the plug 225 may be formed from any material with desired thermal and dielectric properties, e.g. glass fiber, plastic, rubber, etc. The plug 225 may also be formed from liquid products that are dispensed into the hollow fuse tube cavity 215 and cured in the final orientation, e.g. liquid silicone, epoxy, adhesive, etc. The plug 225 may be secured by compression of the plug within the fuse body 205 by securing against the inner surface of the fuse body 205. The elastic properties of the plug 225 allows the plug to seal the ends 210a, 210b of the fuse body 205, and hold the fuse element 220 in tension. In embodiments, the plug 225 may be secured within the fuse body 205 by adhesives, such as glue, etc.
As shown in
The fuse element 220 is shown in a straightened position in
The arc disc 245 may act as an additional arc suppressant, and adds an additional layer of material for an arc to burn through before compromising the end caps 230a, 230b in a short circuit event. The arc disc 245 may also increase the strength of the end caps 230a, 230b by providing extra material to the underside of the end caps 230a, 230b. The mass of the arc disc 245 may also act as a heat sink, drawing heat away from the fuse element and allowing for cooler operating temperatures. As shown in
As shown in
At block 315, arc discs are placed over the plugs at each end of the fuse body. The arc disc may be placed on an edge at the end of the fuse body, so that the plug is covered. The arc disc includes a notch, which may be straight cut along one side to create a pass-through for the end of the fuse element. The notch may be any cut through in the arc disc to allow the end of the fuse element to extend beyond the fuse body.
At block 320, the ends of the fuse element are folded over across an outer surface of the arc discs. The outer surface is a side of the disc facing away from the fuse body. The end may be folded to lie flat on the arc disc. In embodiments, the bend may be substantially 90°. The ends may substantially cover the outer surface of the arc disc when folded. In embodiments, the fuse element with the folded ends will create a “Z” shape, so that the fuse element is disposed diagonally within the fuse body.
At block 325, the end caps are attached to the ends of the fuse body. The end caps have a hole positioned in the top surface so that the folded end of the fuse element and at least a portion of the arc disc are visible beneath the end cap. The end caps may be attached in any manner, including but not limited to adhesives, snap-on, press fit, and corresponding protrusions and grooves with the fuse body.
Solder is deposited in the hole at block 330, filling the hole and gaps between the arc disc, end of the fuse element and the end cap. The solder creates an electrical connection between the end cap the end of the fuse element, and the arc disc, so that there is a continuous electrical connection through the fuse between the end caps.
As used herein, references to “an embodiment,” “an implementation,” “an example,” and/or equivalents is not intended to be interpreted as excluding the existence of additional embodiments also incorporating the recited features.
The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Furthermore, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize its usefulness is not limited thereto and the present disclosure can be beneficially implemented in any number of environments for any number of purposes. Thus, the claims set forth below are to be construed in view of the full breadth and spirit of the present disclosure as described herein.
