Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF INVENTION
Quick acting miniature electric fuses have been
widely used in various electric and electronic circuits.
In most of these fuses, the fusible element is either soldered
to the ends of the lead wires or it is simply secured thereto
mechanically.
One type of minia'ure fuse is described in United
States Patent No. 3,227,841, issued to Aldens J. Gaia on
January 4, 1966. This fuse comprises a hollow housing made of
an insulating material such as a refractory material, an
electrically non-conductive disc also made of a refractory
material and mounted in said housing and a pair of electrically
conductive terminals extending through a pair of spaced
openings in said disc mounting. The two terminals are partially
enclosed in the housing and a fusible conductor stretches
between the enclosed ends of said terminals and is soldered
thereto at both ends.
Another type of fuse comprises a housing which includes
a base made of an insulating material and a pair of lead wires
passed through the base partially into the housing. Each tip
of the lead wires is bent and a fusible conductor stretches between
these tips with the ends of the fusible elements secured to the
of these tips with the ends of the fusible elements secured to
the respective tips of the lead wires by means of an electrically
~5 conductive paste.
These prior fuses, however, are extremely unstable
since the length of the fusible element is subject to variations,
and evaporation of the electrodes due to arcing heat tends to
prolong the arcing time. Accordingly, these fuses have not been
entirely satisfactory.
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114V963
In another type of fuse which is described in
British Patent No. 969,654, published on September 16, 1964,
the fuse comprises an integral fuse body through which extends
a pair of spaced lead wires projecting beyond opposite ends
of the fuse body, and a fusible element between the two ends
of the lead wires in the fuse body. The fusible element and
the lead wires are wholly embedded in a solid, arc-quenching
filler made of epoxy resin and an imperforate cup-shaped cap
is fitted over the fuse body to encase the fusible element, the
lead wire portions in the fuse body and the epoxy resin filler.
The difficulty with fuses using epoxy fillers,
however, is that, the heat generated by the passage of electric
current causes thermal expansion with subsequent contraction
when current flow is interrupted. Repeated thermal expansions
and contractions often cause breakdown of the fusible element.
Accordingly, it is an object of this invention to
provide a miniature electric fuse which is substantially free
from the aforesaid inherent drawbacks of the prior fuses.
It is a further object of this invention to provide
a miniature electric fuse which is quick acting and has improved
arc-extinguishing characteristic.
It is also an object of this invention to provide
such a fuse which also exhibits improved stability and thermal
capacity.
The foregoing and other objects of this invention
will be described in detail in the ensuing description of the
preferred embodiment of the invention taken in conjunction
with the accompanying drawings.
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63
SUMMARY OF INVENTION
In accordance with this invention a miniature
electric fuse is provided which, due to its unique construction
and arrangement of its component parts, exhibits improved
thermal stability and capacity, and superior arc-quenching
characteristic. The fuse comprises a fuse base and body, a
fuse cover which is fitted onto the fuse body and base, and a
pair of electrically conductive lead wires protruding from
the fuse base and partially embedded into the fuse body. The
fuse body comprises a pair of opposed, spaced apart, generally
crescent-shaped members, each member being defined by an outwardly
curved surface, generally flat top and bottom surfaces and
generally perpendicular inner wall, wherein each of said inner
walls is spaced apart and is in parallel facing relation to one
another. The embedded ends of the electrically conductive
lead wires are disposed midway in each of the respective members
of the fuse body. A groove is cut in each of said members from
the top surface thereof to approximately midway in each member
and thereafter is angled horizontally relative to said
perpendicular inner walls of said members. A fusible element
is stretched between said terminals and has its end portions
resting on the bottom of said grooves and are soldered thereto.
In order to improve the thermal capacity of the fuse,
and to prevent the solder from scattering about in the event
of a fuse blowout, a metal plate (e.g., a brass plate) is
placed on top of the solder surface and is preferably bonded
thereto for added safety.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, wherein like reference numerals are
employed to designate like parts:
~ IG. 1 is a perspective view of the fuse of this
invention capped and ready for installation;
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FIG. 2 is a perspective view of the fuse shown in
FIG. 1 with the fuse cover removed;
, FIG. 3 is a plan view of the fuse shown in FIG. 2
before the fusible element is stretched between the electrodes;
5FIG. 4 is a view similar to FIG. 3 after the fusible
element is stretched betwen the electrodes and soldered;
FIG. 5 is a sectional view taken along the line 5-5
in FIG. 4; and
FIG. 6 is a sectional view taken along the line 6-6
of FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENT OF THE INVENTION
Referring first to FIG. l, there is shown a miniature
electric fuse generally designated as l comprising a fuse
cap or cover 3 capped onto a fuse base 5, and a pair of electrodes
7,7' protruding from the fuse base 5. As shown in FIGS. 5 and
6 the eletrodes 7,7' are embedded into the fuse base and body
as will be more fully described hereinafter.
With reference to FIG. 2, the fuse body comprises a
pair of a generally crescent-shaped substantially identical,
opposed, spaced apart members 9,9' which are defined by curved
outer surfaces 11,11', relatively flat top surfaces 13,13'
and bottom surfaces (not shown) and inner facing walls or
surfaces 15,15' which are spaced apart and substantially
parallel to one another. Each of the electrodes 7,7' extend
through the respective members 13,13' terminating at 17,17'
approximately midway therein as shown in FIGS. 5 and 6.
As is further shown in FIGS. 2 and 3 each of the
members 9,9' has a groove (19,19') cut therein from the top
surface down to approximately the middle of each member and
114~963
then at a right angle toward their respective inner walls
13,13'. A fusible element 21, e.g., an electrically
conductive wire, is stretched between the terminals 17,17'
of the electrodes 7,7' with the ends of the fusible elements
positioned at the bottom of the respective grooves and are
soldered to said electrodes as shown at 23.
Due to the unique construction of the miniature
fuse of this invention and the layout of the fusible element
in said grooves, there is less tendency to arcing when an
overload current passes through the fuse, and whenever arcing
occurs because of excessive current overload, it can be
extinguished more rapidly.
As is further shown in FIGS. 4 and 5, a relatively
flat brass plate 25 of variable thickness is placed on the
surface of the solder 23, in intimate contact therewith, and
may, for example be bonded thereto. The provision of the brass
plate 25 ~or any other equivalent plate) on the solder surface
as aforesaid serves the dual function of imparting greater
thermal capacity to the fuse so as to achieve quicker melting
of the fusible element, and affords a safety factor in that it
prevents the solder from spraying when the fuse blows due to
passage of excessive electric current.
The lead wire portions in the fuse body, the solder
material and the brass plates are completely encased within
an insulated wall 27 which is a part of the fuse base.
Thus, in accordance with this invention, there is
provided an improved quick acting fuse having superior
performance characteristics than the hitherto employed fuses
for similar applications. As it was previously mentioned the
unique layout of the electrically conductive terminals 7,7'
-- 6 --
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and the fusible element 21 substantially reduces arcing
due to current overload through the fuse, and whenever arcing
occurs due to the passage of excessive current, it can be
extinguished more rapidly. Furthermore, the thermal capacity
of the fuse may be increased or decreased by varying the
thickness of the plate 25 which also serves to prevent the
solder from scattering about in the event of a blowout.
While, the fuse of this invention has been described
with a certain degree of particularity, it must be understood
that such description is not intended to restrict or limit the
scope of this invention. Several changes or modifications
can be made in the construction of the fuse which are
nevertheless comprehended from the detailed disclosure herein
and which are~ therefore within the spirit and contemplation
of this invention.
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