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Патент USA US2122820

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July 5, 1938'.
Filed June 12, 1935
:4‘ 30
Patented July 5, 1938
Bruce D. Marshall and Thomas J. McCormick,
Detroit, Mich.
Application June 12, 1935, Serial No. 26,212
5 Claims. ' (Cl. 200-—142)
This invention relates to electric heating de
tions of. the ingredients can be varied tov regulate
vices and more particularly to a heat sensitive - the point at which the fuse disintegrates.
fuse therefor.
An important object of this invention is to
provide a fuse or circuit breaker which is sensitive
to external heat and which when the critical"
temperature is attained immediately disintegrates
into a form which will not interfere with the
working of surrounding parts and which may be
removed, if desired, by simply blowing 'the dis
In the preferred form of the invention, mag
nesium is alloyed with either one or more of the
following metals; aluminum, manganese, cad-r
mium and copper. In these alloys, magnesium
constitutes from 91.8% to 98.5% of the whole
composition. The other metals enter into com
binationwith magnesium in varying proportions.
Each of the metals mentioned above may form
integrated matter away. The fuse consists of such
a composition that when the surrounding tem
perature has attained a certain degree, thev body
the balance of the composition, that is, form 1.5%
to "8.2% of the whole fuse composition. One such
alloy may consist of magnesium and manganese
of the fuse disintegrates into alight, powdery in which magnesium forms 91.8% to 98.5%.while
15 form.“ The resulting powder formation is non
manganese provides the balance of the fuse.
conductiveand will not short the circuit. The
Another form in which the fuse of magnesium,
disintegratic particles are small and light, and‘ alloy may be made is magnesium alloyed with
upon installation of a new fuse, the remains‘ of alluminum and manganese. In this form mag
the old need only be blown away.
nesium likewise forms 90% or more of the whole
Another object of this invention is to provide composition while the balance is made up of.
an improved construction for supporting a fuse aluminum and manganese,
which readily permits the insertion of new fuses.
A still further composition may consist of all
the metals listed above. Magnesium would‘ con
In the embodiment illustrated, the fuse is rod
Y shaped in formation and bridges two supports, stitute substantially 90% or more while. the bal
25 each of which are provided with fastening devices ance would be made up of relatively small pro 25
to releasably secure the ends of the fuse. 'Ifhe portions of all these metals.
fuse supports are adaptable to any type of heat
When a magnesium alloy of that composition
ing devices, and in the embodiment illustrated forms a part of an electric circuit in thermal re
herein it will be noted that the fuse is supported lation to ‘a device which will heat to relatively
high temperature, the alloy will instantly disin
in readily accessible position.‘
Various other objects and meritorious features tegrate into a light powdery form the moment
of the invention will more fully appear from the the critical temperature is reached. In this man
following speci?cation, appended claims, and ac
ner, it forms an excellent fuse for such electrical
companying drawing, wherein;
heating appliances as irons and the like. The
Figure 1 is a side view ‘partly in cross section disintegrated particles are so lightthat any de
showing the internal structure of the iron,
posit that they form may be blown away while the
Figure 2 is a top view of the rear section of the fuse supporting structure is made ready for an
iron with the cover removed,
other fuse. There is no mess nor any disinte
Figure 3 is a. fragmentary plan view of the grated metal parts which are likely to clog the
heating element and the terminals leading there
operating parts of, surrounding mechanism.
to, and
After disintegration, the powdery material is non
Figure 4 is a detail view showing the manner of conductive and it cannot short the circuit.
supporting and securing the fuse.
The fuse is supported in novel position pro
The 'heat sensitive fuse conducts the electric
45 current and when the critical temperature is at
essentially of magnesium alloyed with one or
more metals which will be described in more de
ed portion I4 is cut away adjacent its rear end
- ' vtained immediately disintegrates into a non-con
ductive powdery form.
viding ready access for replacement of a new fuse.
In the drawing, reference numeral I 0 indicates
the body of an electric heating iron. The iron
is provided with an electric heating element 'or
coil I 2 according to the usual design. The weight
This fuse is composed
tail hereinafter. Magnesium forms the major at is to form an enclosure for the electric ter- ,
metal in the alloy and constitutes substantially . minals and the fuse support. The iron illustrated
90% or more of the fuse composition.
It is
preferred that the fuse'of magnesium alloy dis
integrate at temperatures exceeding 1000“ F., but
55 it is to be understood that the relative propor
herein is of the type known generally as a cord
less electric iron, but the invention is adaptable
to any type of iron. Terminals l8 and I9 pro
trudlng from the rear of the iron are adapted to 55
contact live terminals‘ on an iron stand and con
nect a source of electrical power with the heating
element l2. The terminals are insulated from
therethrough. This action affects the metal con
ductors and increases their resistance.
the iron by sheets of insulative material '20, such
skilled in the art and for that reason I intend to
limit myself only within the scope of the ap—
as mica.
One of the exposed ends 22 of the heating coil
is connected directly to the inner end of the ter
minals 18 as shown in Fig. 2. The other exposed
end 24 of the heating coil is connected to. a sup~
porting bracket 25 forming one of a pair of such
brackets for supporting a fuse. This bracket is
L-shaped with the base of the L secured to an
extension 28 of the weighted member ll and in
sulated- therefrom sheets of mica 3|].
A sec
ond fuse supporting bracket 32 is secured direct
ly to the inner end of the terminal l9. Each of
these brackets is bent over and provided with a
flat top as shown in Figure 4. An adjustable
clamping element 34 is secured to the top of each
of these brackets. Each of these clamping de
vices is provided with short turned down edge
portions 36 and a long depending edge portion
38. The short depending portion rests upon the
top of the bracket while the longer depending
edge overhangs the top of the bracket as clearly
shown in Figure 4. A slot 40 is provided in one
of the longer turned over edge portions 38.
Bridging these brackets is rod 42 of fusible mate
rial, such as the magnesium alloy previously de
scribed. The ends of this rod are secured under
the clamping elements 34. One end is inserted
through the slot 4|]. Tightening of the screws H
will securely grip the fuse in position. When a
fuse has been disintegrated by the heat, another
may be inserted by simply releasing the grip
ping action of the elements 34 and inserting a
new rod thereunder. It is to be noted that the
brackets support the rod in a readily accessible
The ends 22 and 24 of the coil are not con
nected through the intermediary of bus bars of
different metal‘to the terminal as is the usual
practice. Instead, they are connected directly to
Various modi?cations will be apparent to those -
pended claims.
We claim:
1. A circuit breaker sensitive to external heat
comprising a rod of magnesium alloy including
substantially 90% or more magnesium and rela
tively small percentages of aluminum and man
2. A heat sensitive electric fuse comprising a
magnesium alloy including magnesium as the
major ingredient and relatively small proportions
of aluminum, manganese, cadmium and copper.
3. A heat sensitive electric circuit breaker
adapted to disintegrate into a non-conductive
powdery form at temperatures exceeding 1000"
F. comprising an alloy of magnesium and man— ;
4. A fuse construction comprising a pair of
conductive vertical supports each having a flat
topped portion, each of said supports provided
with a metal element removably engageable with
the top portion thereof, said elements having a
relative short turned down edge adapted to rest
on said top portions and a relatively long turned
down edge adapted to overhang the edge of said
flat portions, one of‘said overhanging portions I
having a vertical slot, and a heat sensitive fusible
metal rod bridging said supports and having one
end extending through said slot to be releasably
engaged between one support and its cooperat
ing metal element and having its other end like
wise engaged between the other support and its
cooperating metal element.
5. An electric fuse sensitive to external heat
and adapted when the critical temperature is
reached to disintegrate into a light powdery non- , .
conductive substance, said fuse composed of an
alloy of magnesium of which magnesium com
prises the major ingredient and the remainder of
the terminals themselves. Not only is this a less
the composition comprises one or more of the fol
expensive procedure but it prevents an unfa
vorable chemical action between dissimilar metals
particularly when they are exposed to high tem
lowing metals: aluminum, manganese, cadmium
peratures and an electric circuit is delivered
and copper.
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