Field of the Disclosure
[0001] Embodiments of the invention relate to the field of circuit protection devices. More
particularly, the present invention relates to a fuse having insulated plugs that
seal a cavity formed within a fuse body and help to extinguish electrical arcs when
an overcurrent condition occurs.
Background of the Disclosure
[0002] 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 respond with different operating times since 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.
[0003] 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. This may include reducing
the number of components and/or using less expensive components, as well as reducing
the number and/or complexity of associated manufacturing steps.
[0004] Consequently, there is a need to reduce the number of components and/or manufacturing
steps to produce a fuse with improved arc extinguishing characteristics. It is with
respect to these and other considerations that the present improvements have been
needed.
[0005] In FIGS. 6 and 7 of the US patent with number 4,656,453 a cartridge fuse 200 is disclosed.
Fuse 200 comprises a fuse filament 212 angularly disposed in a cylindrical fuse housing
214. The interior surface 215 of housing 214 defines a central linear passageway 220
having two ends in which are secured a pair of resilient cylindrically configured
end plugs 216 and 218. Plugs 216 and 218 are secured in housing 214 by any means desired,
such as by compression of the material thereof, gluing, etc. The ends 224 and 226
of the fuse filament 212 are held captively secured between the exterior surfaces
228 and 230 of the plugs and the interior surface 215 of housing 214 by the resilient
lateral compression of the plug material engaging against the fuse ends for an appreciable
length thereof. The compression of the fuse filament ends 224 and 226 is used to maintain
a light tension along the length of fuse filament 212 between plugs 216 and 218. Two
cup-like, cylindrical conducting end terminal caps 232 and 234 are secured to the
housing 214 by a mechanical engagement of shoulders 240 and retaining grooves 242.
The ends 224 and 226 of fuse filament 212 pass through between the plug surfaces 228
and 230 and housing surface 215 and terminate in tips 244 and 246 folded at right
angles over the outer surfaces of plugs 216 and 218. End caps 232 and 234 close the
ends of housing 214 to leave small chambers 248 and 250 that are filled with solder
to connect electrically the fuse filament tips 244 and 246 to the end caps 232 and
234.
Summary
[0006] The present disclosure is directed to a fuse according to claim 1.
Brief Description of the Drawings
[0007] By way of example, specific embodiments of the disclosed device will now be described,
with reference to the accompanying drawings, in which:
FIG. 1A illustrates a perspective exploded view of an exemplary fuse
FIG. 1B illustrates a side cross sectional view of the fuse shown in FIG. 1A.
FIG. 2A illustrates a perspective exploded view of a fuse embodiment in accordance
with the present disclosure.
FIG. 2B illustrates a side cross sectional view of the fuse shown in FIG. 2A.
FIG. 3 illustrates a logic flow diagram in connection with the fuse shown in FIGS.
1A and 1B.
FIG. 4 illustrates a logic flow diagram in connection with the fuse shown in FIGS.
2A and 2B.
FIG. 5A illustrates a progression of perspective views depicting the formation of
another fuse example.
FIG. 5B illustrates a side view of the fuse shown in FIG. 5A.
FIG. 5C illustrates a side cross-sectional view of the fuse shown in FIG. 5A taken
along lines A-A shown in FIG. 5B.
FIG. 6 illustrates a logic flow diagram in connection with the fuse shown in FIGS.
5A-5C.
FIG. 7A illustrates a perspective exploded view of another example fuse .
FIG. 7B illustrates a perspective view of the fuse shown in FIG. 7A.
FIG. 8A illustrates a side cross sectional view of another example fuse .
FIG. 8B illustrates a perspective view of the fuse element of the fuse shown in FIG.
8A
FIG. 9 illustrates an exploded perspective view of another example fuse .
FIG. 10A illustrates an exploded perspective view of another example fuse .
FIG. 10B illustrates a perspective view of the fuse shown in FIG. 10A.
Detailed Description
[0008] The present invention will now be described more fully hereinafter with reference
to the accompanying drawings, in which preferred embodiments of the invention are
shown. This invention, however, may be embodied in many different forms and should
not be construed as limited to the embodiments set forth herein. Rather, these embodiments
are provided so that this disclosure will be thorough and complete, and will fully
convey the scope of the invention to those skilled in the art. In the drawings, like
numbers refer to like elements throughout.
[0009] Fig. 1A illustrates a perspective exploded view of an exemplary fuse 10. The fuse 10 includes
a fuse body 20 which defines a cavity 25 extending from a first end face 26-A to a
second end face 26-B. The shape of the fuse body 20 can be, for example, rectangular,
cylindrical, triangular, etc., with various cross-sectional configurations. The fuse
body 20 may be formed from an electrically insulative material such as, for example,
glass, ceramic, plastic, etc.
[0010] The fuse 10 includes a fusible element 30 that is disposed within the cavity 25 and
extends in a diagonal orientation from the first end face 26-A of the fuse body 20
to the second end face 26-B. In particular, the fusible element 30 has a first end
30-A which is bent or otherwise made contiguous with the respective end face 26-A
of the fuse body 20 and a second end 30-B which is also bent or otherwise made contiguous
with the respective end face 26-B of the fuse body 20. The fusible element 30 is configured
to melt or otherwise create an open circuit under certain overcurrent conditions.
The fusible element 30 may be a ribbon, a wire, a metal link, a spiral wound wire,
a film, an electrically conductive core deposited on a substrate, or may have any
other suitable structure or configuration for providing a circuit interrupt.
[0011] The fuse 10 also includes insulated plugs 40-A and 40-B which are disposed within
the cavity 25 at respective longitudinal ends of the fuse body 20 to close or plug
openings thereto. In particular, the insulated plugs 40-A and 40-B may be formed of
an insulative adhesive material, such as ceramic adhesive, for example, that is deposited
in the cavity 25 after the fusible element 30 is positioned within fuse body 20 during
manufacture. In addition, the insulated plugs 40-A and 40-B may be positioned to allow
the respective ends 30-A and 30-B of the fusible element 30 to be disposed at least
partially between the plugs 40-A and 40-B and an interior surface of the fuse body
20. The ends 30-A and 30-B may thus extend to, and engage, the end faces 26-A and
26-B, respectively. In particular, a portion 31-A of the fusible element 30 that is
proximate the first end 30-A is positioned between insulated plug 40-A and the interior
surface of the fuse body 20 to allow the end 30-A of the fusible element 30 to protrude
from the cavity 25 and engage the surface 26-A of the fuse body 20. Similarly, the
portion 31-B of the fusible element 30 that is proximate the second end 30-B is positioned
between the insulated plug 40-B and the interior surface of the fuse body 20 to allow
the end 30-B of the fusible element 30 to protrude from the cavity 25 and engage the
surface 26-B of the fuse body 20.
[0012] The fuse 10 includes first 50-A and second 50-B end terminations disposed on the
first 26-A and second 26-B end faces, respectively, of the fuse body 20 which also
cover the insulated plugs 40-A and 40-B. In particular, the first end termination
50-A is in electrical contact with at least the first end 30-A of the fusible element
30 at the end face 26-A and the second end termination 50-B is in electrical contact
with at least the second end 30-B of the fusible element 30 at the end face 26-B.
In this manner, a current path is defined between the end terminations 50-A and 50-B
and the fusible element 30. The first and second end terminations 50-A and 50-B may
be formed of an electrically conductive material, such as silver (Ag) paste or an
electolessly deposited metal such as copper (Cu), applied to the ends of the fuse
body 20 over the insulated plugs 40-A and 40-B. The end terminations 50-A and 50-B
may also be plated with nickel (Ni) and/or tin (Sn) to accommodate soldering of the
fuse 10 to a circuit board or other electrical circuit connection.
[0013] Fig. 1B illustrates a side cross sectional view of the assembled fuse 10. As can be seen,
and as described above, the fusible element 30 is oriented diagonally within the cavity
25 of the fuse body 20 with the first end 30-A disposed on the end face 26-A, and
with the second end 30-B disposed on the end face 26-B. The insulated plug 40-A is
disposed within the cavity 25 with the portion 31-A of the fusible element 30 disposed
between the plug 40-A and the interior surface of the fuse body 20. Similarly, the
insulated plug 40-B is disposed within the cavity 25 with the portion 31-B of the
fusible element 30 disposed between the plug 40-B and the interior surface of the
fuse body 20.
[0014] When an overcurrent condition occurs, the fusible element 30 melts, which interrupts
the flow of current in the circuit (not shown) to which the fuse 10 is connected.
When the fusible element 30 melts, an electric arc may form in a gap or arc channel
that is created between the separated, un-melted portions of the fusible element 30
that remain within the cavity 25. The un-melted portions of the fusible element 30
continue to melt and recede from one another and the arc channel therebetween continues
to grow until the voltage in the circuit is lower than that required to maintain the
arc across the arc channel, at which point the arc is extinguished. The insulated
plugs 40-A and 40-B serve to reduce this arc channel within the cavity 25 by decreasing
the length "d" of the cavity 25 defined between the insulated plugs 40-A and 40-B
relative to conventional fuses having no such insulated plugs, as well as by providing
insulated seals at the longitudinal ends of the fuse body 20 which facilitates the
interruption of fault currents more quickly than conventional fuse configurations.
In addition, it is contemplated that the insulated plugs 40-A and 40-B can be formed
of ceramic adhesive or other insulative materials that do not possess gas evolving
properties. Therefore, when an overcurrent condition occurs and an electrical arc
is generated in the cavity 25, the insulated plugs 40-A and 40-B do not emit gas into
the cavity 25 which could otherwise feed the arc.
[0015] The end termination 50-A is disposed over the end face 26-A of the fuse body 20,
the end 30-A of fusible element 30, and the insulated plug 40-A. Similarly, the end
termination 50-B is disposed over the end face 26-B of fuse body 20, the end 30-B
of the fusible element 30, and the insulated plug 40-B. As described above, the end
terminations 50-A and 50-B may be formed of silver paste that applied to the longitudinal
ends of the fuse body 20. The insulated plugs 40-A and 40-B thus provide a surface
for the end terminations 50-A and 50-B, respectively, to be deposited on. Otherwise,
in the absence of the insulated plugs 40-A and 40-B, multiple applications of a layered
paste, such as, for example, silver paste, would have to be successively deposited
at the ends of the fuse body 20, with each layer being allowed to dry before a subsequent
layer of paste is applied in order to ultimately close or seal the ends of cavity
25 before the end terminations 50-A and 50-B are fully disposed over the respective
end faces 26-A and 26-B. Thus, the use of insulated plugs reduces manufacturing time
and associated costs by providing an application surface for the end terminations
50-A and 50-B and thereby avoiding the need to apply multiple layers of paste to seal
the cavity 25.
[0016] Fig. 2A illustrates an exploded perspective view of an exemplary embodiment of a fuse 100
in accordance with the present disclosure. The fuse 100 includes a fuse body 120 which
defines a cavity 125 extending from a first end face 126-A to a second end face 126-B.
As described above with regard to the fuse 10, the fuse body 120 may be formed from
an electrically insulative material such as, for example, glass, ceramic, plastic,
etc.
[0017] A fusible element 130 is disposed within the cavity 125 and extends from the first
end face 126-A of the fuse body 120 to the second end face 126-B. The fusible element
130 has a first end 130-A which is bent or otherwise made contiguous with the respective
end face 126-A of the fuse body 120 and a second end 130-B which is also bent or otherwise
made contiguous with the respective end face 126-B of the fuse body 120. The fusible
element 130 may be a ribbon, a wire, a metal link, a spiral wound wire, a film, an
electrically conductive core deposited on a substrate, or may have any other suitable
structure or configuration for providing a circuit interrupt. The ends 130-A and 130-B
of the fusible element 130 are shown as being spaced away from the respective end
faces 126-A and 126-B, however, this configuration is shown only for explanatory purposes.
Particularly, the ends 130-A and 130-B of the fusible element 130 are disposed on
the respective end faces 126-Aand 126-B of the fuse body 120 in a manner similar to
the ends 30-A and 30-B described above. The fusible element 130 is configured to melt
or otherwise create an open circuit under certain overcurrent conditions depending
on the fuse rating.
[0018] A metalized coating 160-A is disposed on the end face 126-A of the fuse body 120
and is in electrical contact with the end 130-A of the fusible element 130. Similarly,
a metalized coating 160-B is disposed on the end face 126-B of the fuse body 120 and
is in electrical contact with the end 130-B of the fusible element 130. Notably, the
metalized coatings 160-A and 160-B are not deposited on the interior surface of the
fuse body 120. The metalized coatings 160-A and 160-B assist in forming electrical
connections between the ends 130-A and 130-B of the fusible element 130 and the respective
end terminations 150-A and 150-B as further described below.
[0019] Insulated plugs 140-A and 140-B are disposed within the cavity 125 at respective
longitudinal ends of the fuse body 120. As described above with regard to the fuse
30, the insulated plugs 140-A and 140B may be formed of an insulative adhesive material,
such as ceramic adhesive, that is deposited within the cavity 125 after the fusible
element 130 is positioned within fuse body 120 with the ends 130-A and 130-B disposed
on the respective end faces 126-A and 126-B. The insulated plugs 140-A and 140-B may
be positioned to allow the respective ends 130-A and 130-B of the fusible element
130 to be disposed at least partially between the plugs 140-A and 140-B and an interior
surface of the fuse body 120. The ends 130-A and 130-B may thus extend to, and engage,
the end faces 126-A and 126-B, respectively. The metalized coatings 160-A and 160-B
are applied to the end faces 126-A and 126-B as described above.
[0020] The fuse 100 includes first 150-A and second 150-B end terminations disposed on the
first 126-A and second 126-B end faces of the fuse body 120 which also cover the respective
insulated plugs 140-A and 140-B. In particular, the first end termination 150-A is
in electrical contact with the end 130-A of the fusible element 130 and the metalized
coating 160-A at the end face 126-A of the fuse body 120. Similarly, the second end
termination 150-B is in electrical contact with the end 130-B of the fusible element
130 and the metalized coating 160-B at the end face 126-B of the fuse body 120. In
this manner, a current path is defined between the end terminations 150-A and 150-B
and the fusible element 130 via the metalized coatings 160-A and 160-B. The first
and second end terminations 150-A and 150-B may be formed of an electrically conductive
material, such as silver (Ag) paste or an electrolessly deposited metal such as copper
(Cu), applied to the ends of the fuse body 120 over the insulated plugs 140-A and
140-B. The end terminations 150-A and 150-B may also be plated with nickel (Ni) and/or
tin (Sn) to accommodate soldering of the fuse 100 to a circuit board or other electrical
circuit connection.
[0021] Fig. 2B illustrates a side cross sectional view of the assembled fuse 100 wherein the fusible
element 130 is oriented diagonally within the cavity 125 of the fuse body 120 with
the end 130-A disposed on end face 126-A and the end 130-B disposed on end face 126-B.
As described above, the metalized coating 160-A is disposed on the face 126-A and
forms an electrical connection between the end 130-A of the fusible element 130 and
the end termination 150-A. Similarly, the metalized coating 160-B is disposed on the
end face 126-B and forms an electrical connection between the end 130-B of the fusible
element 130 and the end termination 150-B. The insulated plug 140-A is disposed within
the cavity 125 which seals the cavity 125 from the end termination 150-A and the insulated
plug 140-B is disposed within the cavity 125 which seals the cavity 125 from the end
termination 150-B.
[0022] When an overcurrent condition occurs, the fusible element 130 melts which interrupts
the circuit (not shown) to which the fuse 100 is connected. When the fusible element
130 melts, an electric arc may form in a gap or arc channel that is created between
the separated, un-melted portions of the fusible element 130 that remain within the
cavity 125. The un-melted portions of the fusible element 130 continue to melt and
recede from one another and the arc channel therebetween continues to grow until the
voltage in the circuit is lower than that required to maintain the arc across the
arc channel, at which point the arc is extinguished. The insulated plugs 140-A and
140-B serve to reduce this arc channel within the cavity 125 by decreasing the length
of the cavity 125 defined between the insulated plugs 140-A and 140-B relative to
conventional fuses having no such insulated plugs, as well as by providing insulated
seals at the longitudinal ends of the fuse body 120 which facilitates the interruption
of fault currents more quickly than conventional fuse configurations. In addition,
it is contemplated that the insulated plugs 140-A and 140-B can be formed of ceramic
adhesive or other insulative materials that do not possess gas evolving properties.
Therefore, when an overcurrent condition occurs and an electrical arc is generated
in the cavity 125, the insulated plugs 140-A and 140-B do not emit gas into the cavity
125 which could otherwise feed the arc.
[0023] Included herein are flow chart(s) representative of exemplary methodologies for performing
novel aspects of the present disclosure. While, for purposes of simplicity of explanation,
the one or more methodologies shown herein, for example, in the form of a flow chart
or logic flow, are shown and described as a series of acts, it is to be understood
and appreciated that the methodologies are not limited by the order of acts, as some
acts may, in accordance therewith, occur in a different order and/or concurrently
with other acts from that shown and described herein. For example, those skilled in
the art will understand and appreciate that a methodology could alternatively be represented
as a series of interrelated states or events. Moreover, not all acts illustrated in
a methodology may be required for a novel implementation.
[0024] Fig. 3 illustrates an example of a logic flow 300 in connection with the fuse 10 shown in
Figs. 1A and
1B. A fusible element 30 is threaded through the fuse body at step 310. For example,
the fusible element 30 is threaded through the fuse body 20 with the ends 30-A and
30-B being disposed on the end faces 26-A and 26-B. A ceramic adhesive is deposited
within the cavity 25 at the longitudinal ends of the fuse body 20 at step 320. The
ceramic adhesive adheres to the interior surface of the fuse body 20 and serves to
close or seal the ends of the cavity 25. The adhesive is dried at, for example, 150°C
for a predetermined time period at step 330. End terminations 50-A and 50-B, such
as may be formed of a silver paste or an electrolessly deposited metal such as copper,
are applied to each end of fuse body 20 at step 340. The end terminations 50-A and
50-B may be dried at 150°C and sintered at 500°C at step 350. The end terminations
50-A and 50-B may be plated with Nickel (Ni) and/or Tin (Sn) at step 360 to accommodate
solderability of the fuse 10 to one or more electrical connections within a circuit.
[0025] Fig. 4 illustrates an example of a logic flow 400 in connection with the fuse 100 shown
in
Figs. 2A and
2B. A fusible element 130 is threaded through the fuse body at step 410. For example,
the fusible element 130 is threaded through the fuse body 120 with the ends 130-A
and 130-B of the fusible element 130 being disposed on the end faces 126-A and 126-B.
A metalized layer is deposited on the end faces 126-A and 126-B of the fuse body 120
at step 420. A ceramic adhesive is deposited within the cavity 125 at the longitudinal
ends of the fuse body 120 at step 430. The ceramic adhesive adheres to the interior
surface of the fuse body 120 and serves to close or seal the longitudinal ends of
the cavity 125. The adhesive is dried at, for example, 150°C for a predetermined time
period at step 440. End terminations 150-A and 150-B, such as may be formed of silver
paste or an electrolessly deposited metal such as copper, are applied to each end
of the fuse body 120 at step 450.
[0026] Fig. 5A illustrates an exploded perspective view of an exemplary fuse 500. The fuse 500 includes
a fuse body 520 which defines a cavity 525 extending from a first end face 526-A to
a second end face 526-B. As described above with regard to the fuse 10, the fuse body
520 may be formed from an electrically insulative material such as, for example, glass,
ceramic, plastic, etc.
[0027] A fusible element 530 is disposed within the cavity 525 and extends from the first
end face 526-A of the fuse body 520 to the second end face 526-B. The fusible element
530 has a first end 530-A which is bent or otherwise made contiguous with the respective
end face 526-A of the fuse body 520 and a second end 530-B which is also bent or otherwise
made contiguous with the respective end face 526-B of the fuse body 520. The fusible
element 530 may be a ribbon, a wire, a metal link, a spiral wound wire, a film, an
electrically conductive core deposited on a substrate, or may have any other suitable
structure or configuration for providing a circuit interrupt.
[0028] The fusible element 530 may include a center kink 535 which may also have one or
more holes formed through it to serve as a weak connection area. The kinked portion
535, located generally at the center of the fusible element 530, provides a means
for relieving stress, including both expansion and compression stresses, which may
be produced in the fusible element 530 during a thermal cycle that could otherwise
cause premature breakage of the element 530. The fusible element 530 is configured
to melt or otherwise create an open circuit under certain overcurrent conditions depending
on the fuse rating.
[0029] A metalized coating 560-A is disposed on the end face 526-A of the fuse body 520
and is in electrical contact with the end 530-A of the fusible element 530. Similarly,
a metalized coating 560-B is disposed on the end face 526-B of the fuse body 520 and
is in electrical contact with the end 530-B of the fusible element 530. Notably, the
metalized coatings 560-A and 560-B are not deposited on the interior surface of the
fuse body 520. The metalized coatings 560-A and 560-B assist in forming electrical
connections between the ends 530-A and 530-B of the fusible element 530 and the respective
end terminations 550-A and 550-B as further described below.
[0030] Insulated plugs 540-A and 540-B are disposed within the cavity 525 at respective
longitudinal ends of the fuse body 520. As described above with regard to the fuse
530, the insulated plugs 540-A and 540B may be formed of an insulative adhesive material,
such as ceramic adhesive, that is deposited within the cavity 525 after the fusible
element 530 is positioned within the fuse body 520, with the ends 530-A and 530-B
extending through the plugs 540-A and 540-B and disposed on the respective end faces
526-A and 526-B. Particularly, since the plug 540-A may be an adhesive applied to
the cavity 525, the fusible element 530, positioned within the fuse body 520, is surrounded
by the adhesive that comprises the plug 540-A. In this manner, the end 530-A of the
fusible element 530 extends through the adhesive plug 540-A and also extends outside
the fuse body 520. Similarly, since the plug 540-B may be made from an adhesive applied
to the cavity 525, the fusible element 530, positioned within fuse body 520, is surrounded
by the adhesive that comprises the plug 540-B. In this manner, the end 530-B of the
fusible element 530 extends through the adhesive plug 540-B and also extends outside
of the fuse body 520. Each of the ends 530-A and 530-B of the fusible element 530
may be bent or crimped along the respective end surfaces 526-A and 526-B of the fuse
body 520 as described above. The metalized coatings 560-A and 560-B are then applied
to the end faces 526-A and 526-B as described above.
[0031] The fuse 500 includes first 550-A and second 550-B end terminations disposed on the
first 526-A and second 526-B end faces of fuse body 520 which also cover the respective
insulated plugs 540-A and 540-B. In particular, the first end termination 550-A is
in electrical contact with the end 530-A of the fusible element 530 and the metalized
coating 560-A at the end face 526-A of the fuse body 520. Similarly, the second end
termination 550-B is in electrical contact with the end 530-B of the fusible element
530 and the metalized coating 560-B at the end face 526-B of the fuse body 520. In
this manner, a current path is defined between the end terminations 550-A and 550-B
and the fusible element 530 via the metalized coatings 560-A and 560-B. The first
and second end terminations 550-A and 550-B may be formed of an electrically conductive
material, such as silver (Ag) paste or an electrolessly deposited metal such as copper
(Cu), applied to the ends of the fuse body 520. The end terminations 550-A and 550-B
may also be plated with nickel (Ni) and/or tin (Sn) to accommodate soldering of the
fuse 500 to a circuit board or other electrical circuit connection.
[0032] Fig. 5B illustrates a side view of the assembled fuse 500 including the fuse body 520 with
the ends 530-A and 530-B of the fusible element 530 extending from the fuse body 520
along the end surfaces 526-A and 526-B, respectively. The electroless plated first
end termination 550-A and second end termination 550-B are located at the respective
ends of fuse body 520 and extend over the first 526-A and second 526-B end faces as
well as cover the insulated plugs 540-A and 540-B (not shown).
[0033] Fig. 5C illustrates a cross-sectional view of the assembled fuse 500 taken along lines A-A
shown in
Fig. 5A. As can be seen, the fusible element 530 is disposed within the cavity 525 of the
fuse body 20 and extends through the insulated plugs 540-A and 540-B with the end
530-A disposed on the end face 526-A, and the end 530-B disposed on the end face 526-B.
In particular, the end 530-A of the fusible element 530 extends through the plug 540-A,
and the end 530-B of the fusible element 530 extends through the plug 540-B. The end
530-A is crimped or bent to extend along the surface of the end face 526-A. Similarly,
the end 530-B is crimped or bent to extend along the surface 526-B.
[0034] When an overcurrent condition occurs, the fusible element 530 melts which interrupts
the circuit to which the fuse 500 is connected. When the fusible element 530 melts,
an electric arc may form in a gap or arc channel that is created between the separated,
un-melted portions of the fusible element 530 that remain within the cavity 525. The
un-melted portions of the fusible element 530 continue to melt and recede from one
another and the arc channel therebetween continues to grow until the voltage in the
circuit is lower than that required to maintain the arc across the arc channel, at
which point the arc is extinguished. The insulated plugs 540-A and 540-B serve to
reduce this arc channel within the cavity 525 by decreasing the length "d" of the
cavity 525 defined between the insulated plugs 540-A and 540-B relative to conventional
fuses having no such insulated plugs, as well as by providing insulated seals at the
longitudinal ends of the fuse body 520 which facilitates the interruption of fault
currents more quickly than conventional fuse configurations. In addition, it is contemplated
that the insulated plugs 540-A and 540-B can be formed of ceramic adhesive or other
insulative materials that do not possess gas evolving properties. Therefore, when
an overcurrent condition occurs and an electrical arc is generated in the cavity 525,
the insulated plugs 540-A and 540-B do not emit gas into the cavity 525 which could
otherwise feed the arc.
[0035] Fig. 6 illustrates an example of a logic flow 600 in connection with the fuse 500 shown
in
Figs. 5A-5C. The fusible element 530, having a kinked portion 535 with holes formed therethrough,
is threaded through the fuse body 520 at step 610. For example, the fusible element
530 is threaded through the fuse body 520 with the ends 530-A and 530-B being disposed
on the end faces 526-A and 526-B. An insulative adhesive, such as a ceramic adhesive,
is deposited within the cavity 525 at the longitudinal ends of fuse body 520 at step
620 to form respective adhesive plugs 540-A and 540-B. The adhesive adheres to the
interior surface of the fuse body 520 and serves to close or seal the longitudinal
ends of the cavity 525 with the ends 530-A and 530-B of the fusible element 530 extending
through the adhesive plugs 540-A and 540-A. The adhesive is dried for a predetermined
time period at step 630. The end terminations 550-A and 550-B, which may be formed,
for example, of silver paste or an electrolessly deposited metal such as copper, are
applied to each end of the fuse body 520 at step 640. The end terminations 550-A and
550-B are dried at step 650. The end terminations 550-A and 550-B may be plated with
Nickel (Ni) and/or Tin (Sn) at step 660 to accommodate solderability of the fuse 500
to one or more electrical connections within a circuit.
[0036] Figs. 7A and
7B illustrate an exemplary fuse 700. As with the fuse 10 described above, the fuse 700
includes a fuse body 720 which defines a cavity 725 extending from a first end face
726-A to a second end face 726-B. The shape of the fuse body 720 can be, for example,
rectangular, cylindrical, triangular, etc., with various cross-sectional configurations.
The fuse body 720 may be formed from an electrically insulative material such as,
for example, glass, ceramic, plastic, etc.
[0037] The fuse 10 further includes a fusible element 710 that may be a thinned portion
of a relatively thicker conductor 705, such as may be formed by subjecting the conductor
705 to a conventional coining process. The fusible element 710 is configured to melt
or otherwise create an open circuit under certain overcurrent conditions in the manner
discussed above with respect to the fusible element 30. Unlike the fusible element
30, the fusible element 710 is formed with a corrugated, wave-like shape to relieve
the element 710 from thermal stresses that could otherwise cause premature breakage
of the element 710 during a thermal cycle. Moreover, the corrugation of the fusible
element 710 results in nonlinearity of adjacent segments of the fusible element 710.
That is, adjacent segments of the fusible element 710 are not coplanar. Thus, if the
fusible element 710 begins to melt or separate at two or more points along its length,
such as during the occurrence of an overcurrent condition, the electrical arcs that
form at the points of separation are also not coplanar and are therefore less likely
to combine and form larger electrical arcs. The detrimental effects of electrical
arcing are thereby mitigated by the corrugated fusible element 710.
[0038] The conductor 705 and fusible element 710 are disposed within the cavity 725 which
extends from the first end face 726-A of the fuse body 720 to the second end face
726-B. In particular, the conductor 705 has a first end 705-A which is bent or otherwise
made contiguous with the respective end face 726-A of the fuse body 720 and a second
end 705-B which is also bent or otherwise made contiguous with the respective end
face 726-B of the fuse body 720.
[0039] Insulated plugs 740-A and 740-B are disposed within the cavity 725 at respective
longitudinal ends of the fuse body 720. As described above with regard to the fuse
10, the insulated plugs 740-A and 740B may be formed of an insulative adhesive material,
such as ceramic adhesive, that is deposited within the cavity 725 after the fusible
element 710 is positioned within fuse body 720, with the ends 710-A and 710-B extending
through the plugs 740-A and 740-B and disposed on the respective end faces 726-A and
726-B. Particularly, since the plug 740-A may be an adhesive applied to the interior
of the cavity 725, the conductor 705 which is positioned within the fuse body 720,
is surrounded by the adhesive that comprises the plug 740-A. In this manner, the end
705-A of the conductor 705 extends through the adhesive plug 740-A and also extends
outside the fuse body 720. Similarly, since the plug 740-B may be made from an adhesive
applied to the interior of the cavity 725, the conductor 705 which is positioned within
fuse body 720 is surrounded by the adhesive that comprises the plug 740-B. In this
manner, the end 705-B of the conductor 705 extends through the adhesive plug 740-B
and also extends outside of the fuse body 720. Each of the ends 705-A and 705-B of
the conductor 705 may be bent or crimped along the respective end surfaces 726-A and
726-B of the fuse body 720 as described above.
[0040] Unlike the fuses 10, 100, and 500 described above, the fuse 700 does not include
end terminations at the first 726-A and second 726-B end faces of the fuse body 720
for providing electrical connections to external circuit elements. Instead, the relatively
thicker portions of the conductor 705, located outside of the fuse body 720, provide
direct connection to other circuit elements.
[0041] Figs. 8A and
8B respectively illustrate an exemplary fuse 800 and corresponding conductor 805 defining
a fusible element 810.
[0042] The fuse 800 includes a fuse body 820 which defines a cavity 825 extending from a
first end face 826-A to a second end face 826-B. The conductor 805 is disposed within
the cavity 825. The shape of the fuse body 820 can be, for example, rectangular, cylindrical,
triangular, etc., with various cross-sectional configurations. The fuse body 820 may
be formed from an electrically insulating material such as, for example, glass, ceramic,
plastic, etc.
[0043] The fusible element 810 is a thinned portion of a relatively thicker conductor 805,
such as may be formed by subjecting the conductor 805 to a conventional coining process.
The fusible element 810 is configured to melt or otherwise create an open circuit
under certain overcurrent conditions in the manner discussed above with respect to
the fusible element 30. Like the fusible element 710 described above, the fusible
element 810 is formed with a corrugated, wave-like shape to relieve the element 810
from thermal stress that could otherwise cause premature breakage of the element 810
during a thermal cycle. Moreover, the corrugation of the fusible element 810 results
in nonlinearity of adjacent segments of the fusible element 810. That is, adjacent
segments of the fusible element 810 are not coplanar. Thus, if the fusible element
810 begins to melt or separate at two or more points along its length, such as during
the occurrence of an overcurrent condition, the electrical arcs that form at the points
of separation are also not coplanar and are therefore less likely to combine and form
larger electrical arcs. The detrimental effects of electrical arcing are thereby mitigated
by the corrugated fusible element 810.
[0044] The fuse 800 also includes insulated plugs 840-A and 840-B which are disposed within
the cavity 825 at respective longitudinal ends of the fuse body 820. The insulated
plugs 840-A and 840-B may be formed of an insulating adhesive, such as ceramic adhesive,
disposed in the cavity 825 to close or seal openings thereto at respective longitudinal
ends of the fuse body 820. In particular, the insulated plugs 840-A and 840-B may
be dispensed in the cavity 825 after the fusible element 810 is positioned within
fuse body 820. The insulated plugs 840-A and 840-B may be positioned to allow respective,
relatively thicker end portions 805-A and 805-B of the conductor 805 to be disposed
through the plugs to allow the end portions 805-A and 805-B to extend longitudinally
beyond the end surfaces 526-A and 526-B, respectively. Particularly, since the plug
840-A may be an adhesive applied to the cavity 825, the end portion 805-A, positioned
within the fuse body 820, is surrounded by the adhesive that comprises the plug 840-A.
In this manner, the end portion 805-A of the conductor 805 extends through the adhesive
plug 540-A and also extends outside the fuse body 820. Similarly, since plug 840-B
may be made from an adhesive applied to the cavity 825, the end portion 805-B, positioned
within fuse body 820, is surrounded by the adhesive that comprises the plug 840-B.
In this manner, the end portion 805-B of the conductor 805 extends through the adhesive
plug 840-B and also extends outside of the fuse body 820.
[0045] The fuse 800 includes first 850-A and second 550-B end terminations located at the
first 826-A and second 826-B end faces, respectively, of the fuse body 820 which also
cover the insulated plugs 840-A and 840-B. In particular, the end termination 850-A
is disposed on a respective end of the fuse body 820 and is in electrical contact
with at least the end portion 805-A of the conductor 805 at the end face 826-A. Similarly,
the end termination 850-B is disposed over a respective end of the fuse body 820 and
is in electrical contact with at least the end portion 805-B of the conductor 805
at the end face 826-B. In this manner, a current path is defined between the end terminations
850-A and 850-B and the fusible element 810. The first and second end terminations
850-A and 850-B may be formed of an electrically conductive material, such as silver
(Ag) paste or an electrolessly deposited metal such as copper (Cu), applied to the
ends of the fuse body 820. The end terminations 850-A and 850-B may also be plated
with nickel (Ni) and/or tin (Sn) to accommodate soldering of the fuse 800 to a circuit
board or other electrical circuit connection.
[0046] Fig. 9 illustrates an exemplary fuse 900. The fuse 900 and method of making the same are
substantially similar to the fuse 10 and the method of making fuse 10 as described
above. Particularly, the fuse 900 includes a fusible element 910, a fuse body 920,
insulated plugs 940-A and 940-B, and electroless plated terminations 950-A and 950-B
that are disposed and interconnected in substantially the same manner as the fusible
element 30, fuse body 20, insulated plugs 40-A and 40-B, and end terminations 50-A
and 50-B of the fuse 10.
[0047] The fusible element 910 is configured to melt or otherwise create an open circuit
under certain overcurrent conditions in the manner discussed above with respect to
the fusible element 30. However, unlike the fusible element 30, the fusible element
910 of the fuse 900 is formed with a corrugated, wave-like shape, like fusible elements
710 and 810 described above, to relieve the element 910 from thermal stresses that
could otherwise cause premature breakage of the element 910 during a thermal cycle.
The fusible element 910 may also have one or more holes 960 formed therethrough to
provide weak connection areas. Thus, if the fusible element 910 begins to melt or
separate at two or more of the holes 960, such as during the occurrence of an overcurrent
condition, the electrical arcs that form at the holes 960 are also not coplanar and
are therefore less likely to combine and form larger electrical arcs. The detrimental
effects of electrical arcing are thereby mitigated by the corrugated fusible element
910.
[0048] Figs. 10A and
10B illustrate yet another exemplary fuse 1000. The fuse 1000 is substantially similar
to the fuse 900 described above, and similarly includes a fuse body 1020 and a corrugated,
wave-shaped fuse element 1010 having holes formed therethrough to provide the element
1010 with weak connection areas and to mitigate the formation of electrical arcs as
described above. However, unlike the fuse 900, the fuse 1000 does not include insulated
plugs or separate, electroless plate terminations. Instead, the fuse 1000 includes
a fuse element 1010 that terminates at both ends in contiguous termination plates
1030-A and 1030-B. The fuse 1000 further includes a two-piece fuse body 1020 having
generally U-shaped base 1040-A and cover 1040-B portions that are configured to fit
together to form an enclosure. The base portion 1040-A may include a pair of longitudinally-spaced
bosses 1050 extending upwardly from an interior surface thereof, and the fuse element
1010 and cover portion 1040-B may include correspondingly positioned pairs of holes
1060 and 1070 formed therethrough for receiving the bosses 1050 as further described
below. The base 1040-A and cover 1040-B portions may be formed of an electrically
insulative material such as glass, ceramic, plastic, etc.
[0049] When the fuse 1000 is operatively assembled as shown in
Fig. 10B, the fuse element 1010 is sandwiched between the base portion 1040-A and the cover
portion 1040-B and fits within a cavity or channel 1080 defined therebetween, with
the bosses 1050 extending upwardly through the holes 1060 and 1070. The bosses 1050
may thereafter be heat staked in order to achieve an interference fit between the
bosses 1050 and the cover portion 1040-B, thereby firmly securing the base portion
1040-A, the fuse element 1010, and the cover portion 1040-B together. With the fuse
1000 assembled thusly, the termination plates 1030-A and 1030-B of the fuse element
1010 protrude from the fuse 1020 and flatly abut respective ends of the fuse body
1020. The termination plates 1030-A and 1030-B thereby accommodate soldering of the
fuse 1000 to a circuit board or other electrical circuit connection. It will be appreciated
that many other means for fastening the base portion 1040-A and the cover portion
1040-B of the fuse body 1020 together may be substituted for the heat-staked bosses
1050 described above. For example, the base portion 1040-A and the cover portion 1040-B
may be fastened together via snap fit or by using mechanical fasteners or adhesives.