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Publication numberUS620309 A
Publication typeGrant
Publication dateFeb 28, 1899
Filing dateApr 27, 1898
Publication numberUS 620309 A, US 620309A, US-A-620309, US620309 A, US620309A
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
William s
US 620309 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

No. 620,309. Patented Feb. 28, I899,

w. s. HADAWAY, JR.


(Application filed Apr. 27, 1898.)

(No Model.)




s-Ls'c'i'mc FUSE..

srncrmcanox formi m of Letters Patent No. 620,309, dated February 28, 1899.

Application filed Apri127,1898.

. J r.-, a citizen of the United States,.residing at NewYor-k, county of Newliorli, State of New York, have inventedcertain new and useful Improvements in Electric Fuse, fully described and represented in the following specification and the accompanying drawings, forming a part of the same.

The object f the present improvement is to secure the conversion of the fuse wire or strip into an insulating substance below the temperature at which the fuse will melt and tothus avoid the formation and dispersion of heated particles which may do injury to surrounding objects. This result is obtained in the present invention by employing the metal magnesium to constitute the entire fuse or as a coating for a fuse-strip of other metal, as

copper, the magnesium in the latter case producing a decomposition of the copper with great rapidity and at a definite temperature greatly below that at which the copper would fuse. I have discovered that magnesium will combine rapidly with the oxygen of the atmosphere when heated by the electric current to a temperature which isbelow the meltingpoint'of the magnesium. The oxidation of the metal progresses at-a more rapid rate when the air is under a pressuregreater than that of the atmosphere, and such increased pressure is secured in thepresent invention by confining the fuse-wire in a tight chamber in which the pressure of the contained air isincreased by the heat generated in the fuse.v

'The' temperature at which the magnesium is oxidized may be governed with still greater accuracy by coating the magnesium of the fuse with a layer or shell of oxygen-bearing material, such as binoxid of manganese, (MnO which gives up its oxygen at a deli nite temperaturebelow the melting-point of magnesium. When a fusewire or strip conducting a current with high voltage is melted by an excess of current, an arc is sometimes formed between the several particles of the melted metal and is thus extended by ste s over the space between the circuit-termina s. The operation of my fuse is entirely different, as'its whole exterior is first converted into magnesia'by the oxidizing action, thus dimin- Serial so. 878,998. on as.)

ishing the cross-section of the fuse wire or strip and the amount of current carried thereby. wire carries less and less current until the conversion is complete and the current is wholly. interrupted! The high conducting power of copper makes it'most desirable for As the oxidation progresses the entire.

a fuse; but experience hasv shown thata cop-- per fuse is gradually deteriorated by the oxygen of-theatmosphereywhich is combined with the copper at a temperature considerably below that due to its carrying capacity.

The capacity of the. fuse is thus gradually d i. 'minished, so that it is liable to be burned out by a current which it was designed to carry with safety. By coating the copper wire with magnesium its oxidation and deterioration are wholly prevented and it is adapted for use as a fuse at a'temperature far below the meltingpoint of copper by the burning away of the magnesium at such low temperature, which I operates to reduce the carrying capacity of the fuse, while the temperature of the bnrnin g magnesium also raises the temperature (it the copper and produces a rapid oxidation'and conversion of the latter into a non-conductin g substance. The magnesium coatinguponthe copper serves to remove man'yiofthe objections to this type of fuse' in that the temperature produced by the electric. current cannever exceed that of the melting-point of mag nesium, and the combination of the magnesium with the copper furnishes an effective means- 0f varying the time factor with an overload of current, as the time required to burn out the fuse is decreased in proportion as the thickness of the magnesium coating is increased. The fuse is thus converted into a mass of insulating material which forcibly re sists the passage of current and afiojrds no terminals, and my construction is thus peculpoints to conduct an are by steps between the iarly adapted for use with high-voltage cur I rents. To prevent positively the formation of an are between the terminals with currents of high voltage, the chamber in which the fuse (with a limited body of air) is inclqsed may be.

intercepted by'one or more diaphragms of 'in- I sulating material, as compressed fused magnesia or carbid of silicon. The fuse passes {through such diaphragms, and when it is con- IOO verted into magnesia the product fills the perforations in the diaphragms and operates to obstruct the passage of an arc, and thus prevents the formation or maintenance of an are between the terminals.

These improvements will be understood by reference to the annexed drawings, in which- Figure 1 is an elevation, and Fig. 2 a longitudinal section, of a fuse with inclosing tube. Fig. 3 is a longitudinal section of a similar construction with diaphragms inserted in the tube. Fig. 4: is a longitudinal section of an ordinary f use-block with the magnesium wire joined to the circuit-terminals upon screwstuds. Fig. 5 is a longitudinal section of a copper fuse-strip coated with magnesium,

and Fig. 6 is a longitudinal section of such a strip coated with manganese binoxid.

A designates a tube of vulcanized fiber or other insulating substance, and B porcelain plugs cemented in the ends of the tube and.

having the fuse-terminals 0 extended through the same. I find that silicate of soda mixed with fine sand forms a pasty cement adapted togecure the plugs firmly in the ends of the tn e. t

D designates the fuse wire or strip, formed of the metal magnesium and attached to the terminals in any suitable manner. The outer ends of the terminals 0 are formed in any suitable manner to make connection with the circuit-wires, the form shown in the drawings being adapted to clamp in spring-holders in the usual manner. I

The plugsB confine the air within the tube, so that when heated by a rise oftemperature in the fuse the pressure of the air is increased and the oxidation of the metal when com menced at a suitable temperature is more rapid than with air at a normal pressure.

In Fig. 3 four diaphragms are shown inserted within the tube between the plugs B, the diaphragms being readily molded of suitable form with a central perforation to permit the passage of the fuse wire or strip. The wire is fitted snugly to the perforation, so that when itis con verted into magnesia, which results in considerable expansion of its volume, the passage through the diaphragm is closed by the insulating substance thus formed. As the fuse is heated uniformly throughout its entire length when traversed by an excess of current, it is converted simultaneously into magnesia throughout its entire length, and after such conversion there -is nothing remaining within the fuse-tubc to conduct the current or to initiate the formation of an are.

If the fuse wire or strip were broken at an y point during the conversion and an arc were formed at such point, the are would be ultimately broken by the further conversion of the stri p into magnesia and the plugging of the holes in the diaphragms, which would each assist in resisting the passage of the arc.

l have found that the diaphragms perform an additional function in modifying or affecting the time required to discharge or break the fuse, as the wire heats more rapidly when unconfined between its terminals and exposed wholly to the air than when intersected by the diaphragms, which cause it to heat more slowly. Where the fuse without the diaphragms would be broken in one minute with a given current, the interposition of a suitable number of the diaphragms will operate to extend the time to one and a half minutes or two minutes, whichever may be desired. The diaphragms thus adapt the fuse for use with currents of high voltage and serve to regulate the time within which an excess of current may be maintained in the circuit.

Fig. 4 shows the ordinary bug cut-out,havin g a porcelain body F and cover G,with studs H, upon which the terminals C are wound, as well as the ends of the fuse-wire D. In this construction the magnesium wire or strip when converted into magnesia becomes a nonconductor of electricity and heat and furnishes no products of a dangerous character adapted to injure surrounding objects if it be displaced from its supports.

Fig. 5 shows the composite fuse formed of a wire or strip D of copper or other metal with a coating of magnesium D. Such strip may be used in any of the constructions shown, operating as follows: The magnesium burns off when the temperature reaches the intended point, and the combustion of the magnesium raises the temperature of the other metal, which is also being rapidlyraised by the electric current, owing to the burning away of the magnesium. The joint effect of such combustion and of the current upon the copper core is to speedily break the latter and open the circuit.

Fig. 6 shows the composite strip coated with binoxid of manganese D which is preferably applied in a pastyform with any suitable adhesive medium and dried upon the fuse strip, so as to adhere permanently.

All the oxids of manganese give up a part of their oxygen at a temperature which is considerably below the melting-point of magnesium, and the binoxid of manganese when decomposed by heat forms protoxid of manganese and sets free at a definite temperature a proportion of oxygen which unites rapidly with the magnesium and converts it into magnesia. This in the case of the composite wire reduces the carrying capacity of the fuse-strip and increases the temperature of the copper or other metallic core, so as to burn it out rapidly.

The association of the magnesium with the binoxid of manganese produces a fuse whose burning-point can be regulated in the most definite manner, as the decomposition of the oxid occurs at a known point. As the bioxid of manganese operates by combination with the magnesium, it may of course be applied to a solid magnesium fuse-strip like that shown in Fig. 2. A time having a magnesium body or covering may be combined -in Fig. 6, as it consumes less of the binoxid and avoids the use of a confining-tube.

-The composite fuse formed of copper or other metal'with magnesium coating and having a coating of manganese binoxid may be advantageously used within the air-tight tube A, as'shown in Fig. 2, as the copper aflords a conductor of the smallest dimensions'for a given capacity, while the magnesium pre vents the deterioration of the copper and secures the burning of the fuse at a temperature below itsmelting-point and without the formation of an arc, while the binoxid of manganese regulates in the closest manner the temperature at which thecircuit shall be broken.

From the above description it will be seen that the magnesium wire or strip employed a in my construction is not fused or melted at all, although I have termed it a.fuse wire or strip herein, because the term fuse is generally employed for thermal devices for interrupting an electric circuit when an excess of current is formed in the same.

The primary feature of my invention is the use in an electric fuse of magnesium which oxidizes below the point of fusion, and the secondary features of the invention are the use of such magnesium as a coating for copper or'othcr metal and the combination with the magnesium of a coating of manganese binoxid to eilcct the oxidation of the magne sium at a perfectly definite temperature dependent upon the heatingof'the binoxid.

Having thus set forth the nature of the invention, what I claim herein is 1. Inan electric "fuse, a inagnesiumwire or strip employed to couduct and to break the current, and adapted to oxidize below the point of fusion, and. thus forming an infusible conductor under such conditions, substantially as set forth.

2. An electric fuse comprising an insulating-tube with plugs at the ends having fuseterminals projected through the same, a series of magnesia diaphragms fitted within the tube between the plugs and a magnesium wire .or strip extended through the diaphragms,

substantially as herein set forth.

3. An electric fuse of copper or other metal having a coating of magnesium adapted to oxidize below the f using-point of magnesium, and thus to heat the metallic core while diminishing the capacity of the fuse-strip, substantially as herein setforth.

4. An electric fuse having a magnesium body or covering, in combination with an environment of manganese binoxid adapted to furnish oxygen to oxidize the magnesium at a definite temperature, substantially as herein set forth.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.




Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2873327 *Apr 19, 1956Feb 10, 1959Bernstein ElliotCombined fuse and current limiting resistor
US2911504 *May 15, 1958Nov 3, 1959Sigmund Cohn CorpFuse member and method of making the same
US4949062 *Apr 24, 1989Aug 14, 1990Cooper Industries, Inc.Fuse having a non-electrically conductive end bell
Cooperative ClassificationH01H85/165