US1976510A - Fuse plug - Google Patents

Description

C. PECKERMAN FUSE PLUG Filed Aug. 6, 1931 ,7 as. .W

IIIIIIIIIIIIII wwf ATTORNEYS Patented Oct. 9, 1934 4FUSE PLUG Charles Peckerman, New York, N. Y.

Application August 6, 1931, Serial No. 555,501

4 Claims.

My present invention in certain of its broad- -er aspects, is capable of ay wide and varied range of use in connection with fuse plugs in general, but is especially adapted for em- 5 bodiment in a fuse plug of the type which employs a frangible transparent handle portion or top.

`The advantagesfof utilizing a glass topped fuse plug have long .been recognized. Such plugs permit ready inspection of the fusible ele-ments. When a number of plugs are arranged in a common fusebox ready detection of a blown fuse is possibledue to the manner in which the glass becomes discolored from the products of combustion when a fusible element burns out. Furthermore they appeal to the general public ybecause of the fact that many persons fearing electric shocks and overly cautious about replacing fuses,` have 'much more coniidence in handling a glass member than rkthey rwould in handling the ordinary metallic topped plug or metal rimmed plug.

VOne diniculty'which has heretofore. been encountered in connection with the use of plugs of this character, has been the danger of the vglass shattering orcracking when the fusible elementburned. Such shattering occurred because of the sudden generation of an intense heat at the interiorof the glass due to the metallic vapors and other 4products of combustion from the burning fuse, the cracking or shattering tendency being further increased by the sudden expansion of the air within the plug. Such shattering was not only productive of undesirable re hazards, but rendered a broken plug diiiicult to remove without danger of injuring the iingers, unless special tools were used to extract the broken plug from its socket.

An object of the present invention is toretain all of the advantages of using the glass `topped plugs and yet eliminate the danger of shattering the frangible materialwhen a fuse blows. f

Another object is to provide a plug of extremely simple, practical, rugged, durable, inexpensive construction, well suited to meet the requirements of convenient manufacture and facile removal and replacement.

Another object is to accomplishr the foregoing desiderata with but slight change in the .construction of a substantially conventional:- ized type of plug,y the only new element required in accordance with one embodiment of the invention being a small heat absorbing disc of fibrous material, such as cardboard,v asbestos or the like, introduced into the interior of the plug asan incident of its manufacture.

In accordance with a preferred embodiment of the invention, the fusible element has one end anchored as usual to a terminal button secured within a socket member of porcelain or equivalent material. The other end of the fuse extends through the hollow chamber defined by the socket piece and the glass handle portion and is soldered or otherwise secured to the threaded terminal sleeve which encircles the assemblage and clamps the glass. handle to the socket. The above described standard construction is modified by my invention in order to minimize the amount of fusible material which burns when an over--load of current passes therethrough. A small plate of heat absorbent material such as cardboard or thev like extends VV`transversely of the hollow interior of the plug and the fuse is led through a notch in the edge of the plate, carried across the plate closely adjacent the exposed surface of the latter and then out between the socket and the handle to the terminal sleeve. Thus the only portion of the fuse which actually burns, is a short length of wire lying substantially directly upon the cardboard and having a weakened portion therein where ythe break may occur.- Consequently the actual amount of fusible material which burns, is less than in prior types of constructions.

The exposed surface of the cardboard itself may char or become blackened by products of combustion when the fuse element burns, but that section of the fusible element which lies below the cardboard and within the socket, will not burn and in consequence, heat generation will be minimized tosuch an extent that there is no danger of the glass piece cracking.

In accordance with other embodiments of the invention, substantially similar results may be obtained by the use of a transparent Ycardboard disposed above the link or by placing the link between two transparent cardboards.v An essential distinction between this type of construction and prior devices is the fact that the present invention reduces heat generation, and `permits the use of ordinary glass, thus avoiding the necessity for attempting to shield the Vglass from the heat or the need for using specially prepared expensive glass. Y K

The invention may be more fully understood from the following description in connection with the accompanying drawing, wherein: Y

Fig. 1 isv a perspective View of a fuse plug'em bodying the invention,

nate the glass top or handle of the fuse plug. v

This member consists preferably of a manually graspable upper end 11 of any suitable cross section and an integral sleeve portion 12. A socket 13 of porcelain or other insulating material is provided with an external flange 14, adapted to be held in abutting relationship with the end of the sleeve 12 by the use of a threaded metallic terminal sleeve 15, having a flange 16 at one end to engage under the flange 14 and havingkthreaded engagement with the sleeve 12, whereby the ange 14 may be drawn tightly against the end of the sleeve 12 when the sleeve 15 is screwed home. Y

e One end of the fuse 1'? (typically a flat fuse wire with a weakened portion 1711) is attached in conventional fashion as by soldering at 20 to aoterminal button 18 spun into engagement with the bottom of the socket 13 through an opening l9-therein,

As thus far described, the plug may be substantiallyv conventional, the present invention residing more particularly in the manner in which the fuse wire is arranged within the plug, so Athat only a-*small length thereof burns when the fuseblows and the heat generation is minimized. i

Ihave illustrated a heat absorbent disc 21 of cardboard or the like, resting upon ,the -top of the socket 13, the socket tapering inwardly as at I22 ,above the flange 14 and aording a shoulder .23.upon which the cardboard disc rests. yThejfuse 1'7V is trained through a slot 21a at one edge of the disc, `carried across the` upper face of the disc in close -contiguity thereto and then passed between the flange 14 and the end of the sleeve 12, being carried upwardly along the outside of the sleeve and having its end 24 lying within a flattened portion or recess 25 in the sleeve l2. The end of the fuse wire Y projects slightly above the top of the metallic sleeve yl5 and the two may be joined together by soldering as at 26. e f e The end 24 of therfuse soldered in the recess 25 not only assures a good electrical contact between the fuse and the metallic sleeve, but also prevents rotation of the metallic sleeve with respectv to the member 10.

It is not my intention in this application to claim the theory of operation of the apparatus above described. The construction, however, has |been thoroughly tested and it has been demonstrated that the frangible top, even though made of -ordinary molded glass does not shatter or .crack when a fuse blows. Without limiting myself therefore to any definite theory of operation, the` following tentative explanation of the advantageous results obtained, is offered:-

.The length of fuse wire actually exposed for burning is less than in the ordinary fuse Vplug of this character. `The only portion which actually. burns and generates vapor, is that Lrun of Vthe fuse A'directly overlying the cardboard.

Therefore, less heat is generated and the danger of cracking the glass lessened. Furthermore, the cardboard subdivides the otherwise capacious chamber cooperatively defined by the members 10 and 13, into two chambers.

The upper of these two chambers may for the sake of convenience, be termed the combustion chamber, since it is here that the actual burning of the fusible element occurs. The lower chamber may, for the sake of descriptive convenience, be referred to as the cushioning charnber, since when combustion occurs in the upper chamber, and the air therein is suddenly eX- panded, with an effect which is almost explosive, the cardboard disc will yield under the pressure suddenly generated and render the upper chamber substantially expansible to take care of the sudden combustion which occurs therein; This cushioning effect of the lower chamber combined with the cardboard is, of course supplementary to the heat absorbing action of the cardboard or the other fibrous disc which may be utilized'.

A contributing factor is Ibelieved-to be the fact that the. restricted volume of the combustion chamber .together with the discwhichcuts it off from the cushioning chamber, both tend .to vminimize convection currents whichV in the absence of the partition ,forming cardboard, would aid in heating the glass. 1 Y 1 During the burning-of the fuse, the arc s shorter, the period of combustion is consequently shorter, the burning is in some manner choked due to the fact that the burning portion of the fuse vlies directly against the heatV absorbing disc and the result desired is `effected without `in `any way .attempting to shield theL glass itself from the heat. .In otherwords, the desired effect `is obtained not by theuse'of a heat vinsulating medium but by the use of .means to controlandv minimize the heat -which is generated. 1 Y f 1 By using a transparent cardboard disc 20 arranged above the fuse instead of below it as shown in Fig. 5,l heat generation takes place almost entirely within the: socket 13, which will not crack or break, even under extreme heat, yet the advantages of a-visible fuse are retained. Furthermore, even with this form of the inventionk the arc is again choked and much of the heat absorbed by the cardboard.

By using transparent cardboard discs 31, 32 above and below the horizontal run'of the fuse wire (Fig. 6), even more effective heat absorption by the cardboard and choking of the4 arc is accomplished.

YIt will thus be seen that there is herein described Vapparatus in which the several features of this invention are embodied, and which apparatus in its action attains the various objects of the invention and iswell suited to meet the requirements of practical use.

As many changes could be made in the above construction, and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all Vmatter contained in the above description orY shown in the accompanying drawing shall be interpreted-asillustrative and ;not in a limiting sense. 1

Having thus described my invention,.what I claim as new and desire to secure by Letters Patent is as follows: y 1. In a .fuse plug having a frangible top, a fuse lWire and. heat absorbing spark choking plates closely adjacent to and upon opposite sides of that portion of the Wire where a break occurs upon overloading of the fuse.

2. In a fuse plug having a glass top, a fuse Wire and heat absorbing spark choking plates closely adjacent to and upon opposite sides of that portion of the Wire Where a break occurs upon overloading oi the fuse, the upper of said elements being transparent whereby the condition of the fusible element may be observed through the glass top.

3. A glass topped fuse plug, having a fusible

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