US2548290A - Cartridge fuse - Google Patents

Description

April 10, 1951 L. DETCH 2,543,290

' CARTRIDGE FUSE Filed Feb. 15, 1946 3 Sheets-Sheet 1 INV ENT OR.

' Jttawzay April 10, 1951 1.. DETCH 2,548,290

CARTRIDGE FUSE Filed Feb. 15, 1946 5 Sheets-Sheet 2 jg INVENTOR.

April 10, 1951 L. pETcH 2,548,2

CARTRIDGE FUSE I Filed Feb. 15, 1946 3 sheets -sheet 3 Patented Apr. 10, 1951 UNITED STATES PATENT O FF ICE "2,548,290 CARTRIDGE-"FUSE Lewis Detoh, Wilkinsburg, 1a. Application-February 15, 1946, SerialNo." 047.7 37

6 Claims. I

This invention relates to improvements in cartridge fuses and particularly of the knifeblade terminal type provided with a renewable fuse.

One of the primary objects of the present invention is to prevent insuchifuses sudden, direct venting at the ends of thefuses,-of gases generated within-the fuse under overload, short circuit or blowouts, and to momentarilyzretardsuch'venting so as to decrease the extent to which the fusible member will be burned out, and consequently lessen the amount of gas generated by the fuse undersuch-blowou'ts.

Another object of this invention is to providea cartridge type fusehav'ing improved means for venting the interior of the fuse casing torelieve the same from high pressures after ,aishorttcircuit or blowout of the fuse, while at the same time releasing only relatively cool-gases.

Yet another object of the invention is to provide means for controlling the liberation of arc gases and to cool the escaping gases by means of tortuous metallic contacts, thereby preventing the emission of flames through the vents.

Still' another object I of the invention is to provide a cartridge fuse which canbe readily and thoroughly cleaned of fused" metal-incident xto blowing of the fuse. 1

A still further objectoftherinvention-is to 'provide a renewable cartridgefusewithmeans where-'- by the threads i of the fuse link 'retaining screws can be fully protected from fused metal incident to blowing of'the fuse 'link,so'that thesa'me'may be readily unscrewed When'rep'lacing a-fuse link.-

Another object of the invention i's'to provide such fuses with improved means for;rigidlyranchoring the 'endsof the fibre connectingfibarito the tongues of the knife blade terminals.

Further objects of the invention: are to provide a cartridge fuse of the type specified which is simple in-its construction and arrangementswithout complicating the'isam'e so as to prohibitively increasethe'cost of manufacture.

To the accomplishment of these and such other objects as may hereafter appear 'the inv'en-- tion consists of the novel construction, combination and arrangement of parts herein specifically described and illustrated inthe-ac'companying drawings, wherein isshown anembodiment of the'invention, but it is 'to 'be understood that changes, variations and modifications may be resorted to which comewithin the scope of "the claims hereunto appended. M

In the drawings wherein like numeralsofre'feb ence designate corresponding parts throughout the severalviews, y I 1 Figure 1 is a side elevational "outline view of 2 the complete :devi'ce, :partly'ziexposing the interior thereof.

:Fig'ure 2 is a 'iviewin side elevation showing the knife blade terminal assembly partly inserted in the casing, with the end elements partly-disassembled.

Figure 3 is anenlarged. vfragmentary sideeleva tion, partly' in cross-section,v showinganassembled end of the device.

Figure 4 is an enlarged, fragmentary top view of an end of the knife blade terminal assembly.

Figure 5 is an enlarged topplan view ofone ofthe discs-as used in this-invention.

Figure 6 is a sectional view online G-'- 6in. Figure 5.

Figure 7 is an enlarged top plan view of the lipped discs as used in this invention.

Figure 8 is a-sectional view on line -8- -.8 in Fi ure 7.

FigureSis-andsometric view of the channeled member as used for'retaining the fibre barin rigidposition.

Figure 10; is an enlarged, fragmentary side view of the knife blade terminal showing the plain disc and the lipped disc assembled on the tongue end of the terminal.

Figure 11 is' a side view of theknife'blade terminal assembly.

Figure 12 is-a top view of Figure ll.

Figure 13 is an isometric view of one of the endclosures drawn to an enlarged scale.

Figure 1d is a view online l4| 4 inFigure 12.

Figure 1515 a sectional view online l5-l5 in Figure-12. v

v Figure ifi'isa modification ofFigure 4 showing a channeled retaining member for the fibre'bar.

Figure 17 represents a sectional view on line ll-ll'in Figure 16.

Figure 18 is an isometric view of the channeled fibre bar retaining member.

Figure 19 is a fragmentary,longitudinal, crosssectional view of a modification of a cartridge fuse, the knife blade terminal assembly being in outline.

Figure 20 is a top view of Figure 19, partly in outline.

Figure 21 is an enlarged, isometric view of one of the knife blade terminals showing the inner disc and the'outer disc secured to theblade.

Figure 22 is an'enlarged, isometric view of the end closure as used in this modification.

Figure 23 is a detail plan view of theinner disc as used in'this modification.

Figure 24 is a side view of Figure 23.

Figure 25 is a detail plan'view of the outer disc as used in this modification.

'Figure"26"is'a sideview of Figure 25.

In referring to the embodiment of the cartridge fuse 20, 2| represents the usual tubular casing of fibre insulation, having a pair of externally threaded metallic end-sleeves 22 secured to said casing by rivets 23, or otherwise.

A pair of brass caps 24, adapted to be screwed onto said end-sleeves 22, are provided at the outer ends thereof with internal flanges 25, and to provide a finger hold for attaching or removing said caps the outer parts thereof are knurled as indicated by the numeral 26.

The knife blade terminal as shown in Figures 11 and 12 comprises a pair of copper knife blade terminals 21 extending out of the caps 24 and having reduced tongues 28 extending into the sleeves 22 of the fibre casing 2|.

The terminals 21 are connected together by a fibre bar 29 which is attached to the opposing tongues 28 of the terminals. In order to retain said fibre bar 29 rigidly in assembled position I provide a channeled retaining member 30 as shown in Figures 4, 9, ll, 12 and 15 inclusive. This retaining member will be explained later.

As shown in Figure 10, the reduced inner end or tongues 28 of terminals 21 form right angled rear end corners 32 on the wide portions of the terminals. The knife blade terminals 21 are provided with plain spacing discs 33 and lipped spacing discs 34 both of which have a rectangular aperture 35 to snugly accommodate the rectangular tongue ends 28 as shown in Figures 4 and 10.

The plain spacing discs are shown detailed in Figures and 6 and the lipped spacing discs are shown detailed in Figures '7 and 8.

It will be noted that the lips 3| of the lipped spacing disc 34 are rounded to conform to the shape of the edges of the terminals 21 in order to fill the space between the corner 32 of the terminals and the plain disc 33 when in final position as shown in the various figures. In order to permanently retain these discs in position the tongues 28 are upset against discs 33, as indicated by the numeral 36 in Figure 4.

In assembled position, the plain discs 33 fit with a slight clearance around the interior of the end sleeves 22 at the outer ends thereof, while the lipped discs 34 form concentric bosses 31 the purpose of which will be explained later.

The plain discs 33 are provided with a pair of diametrically opposite, peripheral notches 38 serving a purpose also explained later.

End closures 39, as best shown in Figure 13, are provided which fit within the cap 24 and are confined between the flanges 25 of caps 24 and the outer faces of the plain spacing discs 33 of the knife blade assembly. These end closures 39 comprise a pair of annular discs in which 40 represents the outer disc and 4| the inner disc. Said outer disc 4|! is diametrically slotted, as at 42, to snugly fit over the knife blade terminals 21.

Both, the inner disc 4| and the outer disc 40 have the same outside diameter. Disc 4| has a concentric hole 43 slightly larger in diameter than the outside diameter of the lipped spacing discs 34, so as to provide a clearance between the outside diameter of disc 34 and the inside diameter of hole 43 when in assembled position (Fig ure 4).

When assembled, the outer disc 40 and the inn-er disc 4| form the end closure 39 and this is accomplished by riveting both discs together by means of a pair of pin-rivets 44 placed at right angles to the slot 42. The inner disc 4| is also provided with diametrically opposite notches 4 45 which correspond, when assembled, to the ends of the diametrical slot 42 in disc 40.

In Figure 4 it Will be noted, that the pin-rivets 44 extend beyond the inner face 45 of the inner disc 4| and extend also outwardly so that part of said pin-rivets 44 extend into the slots 41 located at the edges 48 of the sleeves 22.

The caps 24, when in final position, completely cover the slots 41 of the end sleeves 22 of fibre casing 2|, and the end closures 39 substantially close the caps 24 on the inner face of the flange 25 thereof.

As heretofore mentioned, channeled members 30 are provided in orde to retain the fibre bar 29 in rigid position, such as shown detailed in Figure 9 or assembled in Figures 4, 11, 12 and 15. These channeled members 30 are made of sheet metal and comprise a rectangular base or web 49 having a central aperture 50 and three right angled sides or flanges 5|, 52 and 53.

The side 52 of the channeled member 30 may be permanently secured to the inner face 54 of the spacing disc 33 by soldering, or otherwise.

As best shown in Figures l1, l2 and 15 the right angled side 52 abuts the inner face 54 of spacing disc 33 and is held thereon permanently as above explained.

Obviously, the fibre bar 29 serves mainly as a retaining connection between the two similar ends of the knife blade terminals 21, should the fusible link-member 55 melt after a blow-out. The ends 55 of said fibre bar 29 snugly fit between the angle sides 5| and 53 and for best result the ends 56 should be in abutment with the inner face 51 of said angle side 52.

As will be noted, the aforesaid fusible linkmember 55 contacts one face of the tongues 28 of knife blade terminals 21, while the fibre bar 29 contacts the opposite face of the tongues 28, so that the channeled retaining member 30 embraces the ends of the fibre bar 29 in a manner as shown in Figures 4, ll, 12 and 15.

The fusible link member 55, the fibre bar 29 and the channeled retaining members 30 are securely held to the tongues 23 of the terminals 21 by means of so called drivein machine screws 53 such as shown in Figure 4. These screws are available in the open market and could be used advantageously thereby eliminating undesirable play around the parts and the screw, also resulting in improved electrical connections because the screw-thread 59 of said screw 58 worms itself into the parts and holds very effectively under vibration, impact or shock and wide ranges of temperature conditions to which fuses are subject.

It is to be noted that the fibre connecting bar 29 spaces the knife blade terminals 21 between the shoulders a: as indicated in Figure 12, a distance apart slightly greater than the overall length of the casing 2|, including the end sleeves 22 as part of the casing 2|, see Y in Figure 3, so that when the caps 24 are screwed home on said end sleeves 22 and with the flanges 25 abutting the closures 39, annular gas vents 60, one of which is shown in Figure 3, are provided between the outer ends of said casing 2| and the discs 33 and 34 communicating with the open edges of the slots 41 which are substantially closed, otherwise than at said edges, by the said caps 24 and the end sleeves 22.

As will now be seen, the described fuse is designed to protect instruments connected in, and substances adjacent the circuits and to effect proper-protection, the fusible link member 55 5. must "open the circuits under exact predetermined conditions of overload and short circuit without endangering surrounding iobiects or injury to-the elements of the fuses.

There are three important standard requirements essential in renewablecartridge fuses, first, there must be definite relations between the internal pressure, second, the rate of gas escape and third, the degree to which the gas is cooled before it reaches the-outer atmosphere or surrounding objects.

Under overload, short circuit or blow-outs in the described fuse, the gas may issuefrom the casing 2| around the edges of'the spacing discs 33 and pass into the annular gas vents 60 to the slots 41 in'edges 48 of the end sleeves" and then out'to the atmosphere between the threads of the sleeves 22 and caps 24. Also such gas may seep between the outer discs 49 and inner discs 4| of theend closures 39 to pass into said vents 60 and out of the slot in the same mariner. Some of the gas may also seep by the closures 39 and out of the slots 42 therein.

Thus the gas generated within the fuse is forced to escape by tortuous paths whereby the escape of the gas is retarded sufilciently to prevent large portions of the fusible link member 55 from burning through and thereby generating proportionallylarge quantities'of gas in the fuse.

By designing the gas paths so that the gas generated is conducted through tortuous passages, the gas so deflected into different directions is greatly cooled, due to the mass of metallic contact during the escape. This results in safer operations, under blow-outs, and obviates clogging of the casing and other parts/so that the same maybe easily cleaned when the fusible link member 55 is replaced.

It is to be noted that the described connections of the fusible link member 55 and the fibre bar 29 to the tongues 28 of the knife blade terminals 21 provide for renewing'said link member without loosening the fibre bar 29, as will beclear.

Obviously, the knife blade terminals- 21, the

endclosur'es 39 andthe discs 33 and 34 are interthat the tubular fibre'casing 61 in this modification has been enlarged, the inner spacing disc 68 (Figures 23-24) and the outer spacing disc 69 (Figures 25-26) replace the discs 33 and 34're- 'In order to protect any exposed threads of the screws 58 from melted fuse metal after a blowout I use a cap-nut 6|.

After a short circuit or blow-out the complete fusible link member assembly may be withdrawn from the casing 2| by unscrewing one'of the caps 24. The link member assembly is then thoroughly cleaned andth'e mutilated link member is replaced'by a new one after which the linkassembly is placed into the casing 2| and the cap 24 screwed "home.

Figures 16, 1'7 and 18 show a slight modification of the channeled fibre bar retaining member 30 shown in Figure 9. Y

In this modification the fibre bar retaining member62 comprises a base 63 having -'a pair of opposite upstanding sides 64 to form a channel. A central aperture is provided to accommodate the drivein machine screw 58.

In this construction, the upstanding sides 64- embrace the fibre bar 29 and the tongues 3| of the terminals 21, thereby preventing any movement of bar 29, as will be noted.

It remains now to describe Figures 19 to 26 inclusive,'in which is shown a slight modification of. the cartridge .fuse previously described.

The above mentioned modification relatcs'to spectlvely, shown in Figures 5-6 and 7-8.

End closure 10, shown best in Figure'22, re

placesthe end closure 39 shown in Figure 13 to take care of the larger fibre tube or casing 61 and the inner and outer discs 68 and 69 respectively.

Said inner spacing disc 68 shown detailed in Figures 23' and 24 comprises a flat member having arcuate edges H and parallel straight edges 12. A central slot 13, in -parallel alignment with said edges '12, is provided that fits over the tongue portion 28 of the knife blade terminal 21.

Said outer spacing disc 69, detailed in Figures 25 and 26 comprises a flat member having a circular middle portion 14 narrowed down ends 16, as shown, and having a central slot '15 in parallel alignment with the edges of the narrowed down portion. Both the inner and outer discs 58 and i -59 respectively, are slipped over'the tongueportion 23 of the knifeblade terminal 21, after which the discs are peened, as indicated by the numeral 11, against the shoulder 18 between the tongue 28 and blade terminal 21 (Fig. 19).

Figure22 represents-a perspective view of the end closure 10, as used in this modification, and the same is composed of an annular inner disc 19 and an annular outer disc 80. Said inner disc 19 is provided with a central cut-out portion 8| having a configuration similar to the outline of the outer spacing disc 69, shown detailed in Figure 25, so that the cut-out portion 8| of inner disc-19, when in final position, will clear the contour oflsaid disc 69 in-a manner'asshown in Figures 19 and 20.

The annular outer disc is provided with a centrally disposed, elongated slot 82 which fits over the knifeblade terminal 21.

A'pair of outwardly extending'pins 83 are provided which also serve'to secure "both discs 19 and 89 together. These pins 83 are'spaced apart sufficiently to clear, when assembled, the parallel edges 12 of the inner disc 68 and at the same time penetrate the slots 84 of the end sleeve 85 of the tubular fibre casing 61 to prevent the complete knife blade terminal assembly from turning in the casing.

Atthis time it should be noted, that the heretofore described cartridge fuse is primarily intended to be used for a voltage not to exceed 250, while the herewith described modification is intended to be used for a voltage from 250 to 600 inclusive.

Asis well known in the trade, the vapor generated within the casing 61 by blowing of the fuse member is greater at a high voltage than at a low voltage, and at the same time the internal discs 68 and 69"(Fig. 21 from250 to 600 volts) when assembled with end closures 39 and 1|! re I specti-vely are *designed -to' provide 'a 'baflle to 7 prevent excessive escape of the gases within the cartridge after a blow-out. The lips 3| of disc 34 and the ends I6 of disc 69 respectively serve mainly to provide a long tortuous path for the escaping gases thereby considerably reducing the internal pressure within the cartridge and also reducing the violence of the pressure after a blow-out. In addition, due to the various metallic contacts the gases are considerably cooled when escaping through the gaps between the slot of the cap and the knife blade terminals. Another important feature of the lips of disc 34 has been previously explained.

In order to reduce the vapor generated in a 600 volt cartridge fuse and the internal pressure within the casing in proportion to a 250 volt cartridge fuse, the knife blade terminal of the 250 volt cartridge fuse is made longer and the fibre casing is made larger in diameter.

Since the casing 61 in this modification is longer than the one previously described, the fibre bar 66 and the fusible link member 55 are also longer and in consequence, the discs 68 and 69 shown in Figures 23 to 26 inclusive replace the discs 33 and 34 of the first described cartridge fuse.

The end closure for the 600 volt cartridge fuse shown best in Figure 22 slightly differs from the 250 volt end closure shown in Figure 13, as will be observed.

At this time it should be mentioned that the main reason for enlarging the tubular casing and also lengthen same when using for 600 volts is to provide more space within the casing for the additional vapor generated when blowing a fuse under higher voltage, also retaining sufficient pressure within the casing to aid in quenching the are formed after a fuse blow, but, at the same time, enough vapor must be released to prevent bursting of the fibre casing.

In order to sufficiently cool the vapor before being permitted to escape, the vapor is forced through tortuous paths, as indicated by the arrows in Figures 19 and 20.

The foregoing, it is believed, will suffice to impart a clear understanding of the invention, both as regards structure, cooperation, and the advan tage thereof.

Manifestly, the invention as described, is susceptible of modifications without departing from the invention and right is herein reserved to said modifications as fall within the scope of the appended claims.

What I claim is:

1. A cartridge fuse of the class described, a tubular casing having threaded end sleeves; a removable fuse link supporting structure within said casing; knife blade terminals; an insulating bar for connecting said knife blade terminals; a fuse link member; said terminals having a tongue reduced in width to form a shoulder; a lipped disc and a plain disc, both having a diametrical slot to receive said tongue; said lipped disc in abutment with said shoulder, said plain disc in abutment with said lipped disc, both discs permanently secured to said tongue; said insulating bar attached to one face of said tongue and the fuse link member attached to the other face of said tongue; a channeled bar retaining member having a base and upstanding sides adapted for holding said insulating bar against longitudinal and rotary displacement, one of said upstanding sides in abutment with and secured to the face of said plain disc; an end closure provided with a diametrical slot conforming to a section of said terminal and adapted to receive the lips on the lipped disc and threaded caps screwed onto the threaded end sleeves of said tubular casing.

2. A cartridge fuse comprising a tubular casing of insulating material having a metallic sleeve at each end and a fuse-link supporting structure removably disposed in said casing comprising knife-blade terminals projecting into the outer ends of said sleeves, an insulating bar secured to the inner ends of said terminals and extending through said casing maintaining the terminals in spaced relation, a pair of diametrically slotted discs fitted on each terminal in closely abutting relation, the outer of said discs having circumferentially spaced portions projecting radially outward from the edge thereof, said outer discs having a diameter less than the width of the terminals, diametrically slotted end closures fitted on said terminals outwardly of said discs, each closure having a recess in its inner face shaped to accommodate said outer disc whereby to provide a tortuous escape passage for gases from the interior of said casing, and an annular cap screwed onto each sleeve effective to hold the closure against the outer disc.

3. A fuse as defined by claim 2 characterized by the inne rends of said terminals being reduced in width forming a shoulder thereon and said outer discs abutting said shoulders.

4. A fuse as defined by claim 2 characterized by the sleeves having notches in their outer edges spaced circumferentially thereof and the inner discs having notches in their edges positioned to register with the notches in said sleeves, said closures having inwardly projecting dowel pins positioned to fit into the notches in said inner discs and the notches in said sleeves.

5. A fuse as defined by claim 2 characterized by a channel-shaped retaining member secured to each of the inner discs and embracing the ends of said bar.

6. In a renewable fuse of the class described, a tubular casing having an annular cap threaded onto each end, a fusible link member and a connecting bar within said casing, a knife blade terminal protruding through said caps and having a tongue end adapted to be connected to corresponding ends of said link member and connecting bar, a pair of spacing discs fitted side by side on each of said terminals and means to connect the inner ends of said terminals to corresponding ends of the link member and connecting bar comprising a channeled member provided with a flange secured to the inner disc opposed to the end of the channel member and flanges straddling the end of said connecting bar and a screw extending through each of said channeled members, the tongue end of the adjacent terminal and one end of the link member and connecting bar.

LEWIS DETCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,393,102 Eustice Oct. 11, 1921 1,400,660 Cole Dec. 20, 1921 1,748,480 Hooley Feb. 25, 1930 1,845,756 La Mar Feb. 16, 1932 1,861,744 Johnson June '7, 1932 1,950,489 Glowacki Mar. 13, 1934 1,958,366 La. Mar May 8, 1934

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