US2793269A

US2793269A - Knife blade renewable cartridge fuse

Info

Publication number: US2793269A
Application number: US416502A
Authority: US
Inventors: Detch Lewis
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-03-16
Filing date: 1954-03-16
Publication date: 1957-05-21
Anticipated expiration: 1974-05-21

Description

May 21, 1957 DETCH 2,793,269

KNIFE BLADE RENEWABLE CARTRIDGE FUSE I Filed March 16. 1954 2 Sheets-Sheet l FIG.|

INVEN TOR.

ATTORNEY May 21, 1957 DETCH 2,793,269

KNIFE BLADE RENEWABLE CARTRIDGE FUSE Filed March 16.- 1 954' 2 Shets-Sheet 2 FIG.|3 13 INVENTOR.

ATTORNEY United States Patent KNIFE BLADE RENEWABLE CARTRIDGE FUSE Lewis Detch, Pittsburgh, Pa.

Application March 16, 1954, Serial No. 416,502

11 Claims. (Cl. 200-132) This invention relates to electric circuit breakers, particularly thermal current breakers, and more especially fusible element breakers of the well known thermal type renewable cartridge form.

Those acquainted with the construction, operation and effects of well known knife blade cartridge type fuses are well aware that the insulating bar commonly used to separate the knife blades a precise distance apart is subject to considerable deterioration, especially at the most important portions thereof, that is, at the very ends. This deterioration is due to the quite intense heat to which the insulating bar is often exposed. This intense heat frequently burns or carbonizes the ends of the insulation bar to such an extent that the material thereof crumbles away so that the discs abutting the shoulders of the knife blade and supposedly positioned a fixed predetermined distance apart by the insulating bar, are allowed a certain amount of free motion between the shoulders on the knife blade and the ends of the insulating bar. This free motion of the discs or washers prevents the proper tight closing of the interior of the fuse by the usual collars on the ends of the fuse. The net result is that the venting of the fuse is very seriously interfered with so that the hot gases and molten metal formed when the fuse is subjected to a short circuit current are not properly confined and may issue from the fuse in such manner as to easily ignite adjacent inflammable material.

It is also well known to those acquainted with knife blade cartridge fuses of the usual form that the pressure of the usual collars used for holding the knife blades and interior portions of the fuses in place causes a stress to be placed on the insulating bar tending to cause it to bend or bow and so tilt the usual knife blades in such a manner that they are not in one plane through the longitudinal center line of the fuse. As a consequence, it is often very diflicult to insert such fuses in the usual clip provided therefor.

It is also well known that the contact between the usual fuse link and the usual knife blade is, in most cases, very inefficient with the result that considerable heat may be generated at this point.

It is also well known to those acquainted with cartridge fuses of the usual form that there is frequently the insufficient heat conducting metal in contact with the ends of the fuse links.

It is a principal object of my invention to improve the construction of the usual knife blade cartridge fuses embodying an insulating spacer bar by providing a construction whereby deterioration of the ends of the insulating spacer bar does not result in misalignment of the spacer bar, fuse links, and knife blade and in which the spacing from the face of the usual cartridge closing washers and the usual bolt for retaining the spacer bar and fuse links in place is maintained uniform at all times.

further object of the invention is to provide a device of the type specified in which the method of confining an end of the fuse link to a knife blade will be such that the tendency to generate heat at this point will be decreased and the tendency to distort the ends of the fuse link will be obviated.

A still further object is an improvement in the venting characteristics of the fuse.

Other objects and advantages will appear as the description of the particular physical embodiments selected to illustrate the invention progresses and the novel features will be particularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiment selected to illustrate the invention, reference will be had to the accompanying drawings and the several views thereon, in which like characters of reference designate like parts throughout the several views, and in which:

Fig. 1 is a side elevational view illustrating the usual knife blades and connecting spacer bar of a renewable cartridge fuse, without the usual enclosing cylindrical casing, with my invention includued therein.

Fig. 2 is a view of the device of Fig. 1 at a right angle to the view as shown in Fig. 1.

Fig. 3 is a view of the device as shown by Fig. 1 viewed from the opposite side thereof.

Fig. 4 is a transverse sectional view of the device as shown by Fig. 2 on the plane indicated by the line lV-IV viewed in the direction of the arrows at the ends of the line.

Fig. 5 is a transverse sectional view of the device as shown by Fig. 2 on the plane indicated by the line VV viewed in the direction of the arrows at the ends of the line.

Fig. 6 is a view of a fragment of one end of a fuse link assembly similar to that shown in Fig. 1 illustrating another form of my invention.

Fig. 7 is a longitudinal sectional view of the device of Fig. 6 on the plane indicated by the line VII-.VII viewed in the direction of the arrows at the ends of the line.

Fig. 8 is a transverse sectional view of the device as shown by Fig. 7 on the plane indicated by the line VIII-VIII viewed in the direction of the arrows at the ends of the line.

Fig. 9 is a fragmentary view of one end of a fuse link assembly such as is shown by Fig. 1 illustrating a modified form of my invention.

Fig. 10 is a side elevational view of the device as shown by Fig. 9.

Fig. 11 is a transverse sectional view of the device as shown by Fig. 10 on the plane indicated by the line XI.XI viewed in the direction of the arrows at the ends of the line.

Fig. 12 is a view similar to Figfll but illustrating a "ice modified construction of the device as shown by Fig. 11

Fig. 13 is a fragmentary view of one end of a fuse link assembly such as is shown by Fig. 1 illustrating a modified form of my invention.

Fig. 14 is a transverse sectional view of the device as shown by Fig. 13 on the plane indicated by the line XIV-XIV viewed in the direction of the arrows at the ends of the line.

Fig. 15 is a fragmentary view of one end of a fuse link assembly such as is shown by Fig. 1 illustrating a further modified form of my invention. 7 I

Fig. 16 is a side elevational view of the device as shown by Fig. 15.

Fig- 17 is a transverse sectional view of the device as shown by Fig. 16 on the plane indicated by the line XVIIXVII viewed in the direction of the arrows at the ends of the line.

ln Fig. l, I have shown a fuse link assembly embody in Figs. 2, 3, 4 and 5 there is illustrated the usual pair of

knife blades

1 and 3. Each knife blade has a wider outer end, as 5 and a narrow inner end as 7, best shown in Fig. 3. At the juncture between the wider outer end and the narrow and inner end of each knife blade is a closing end washer, as 9 and 11, formed with

slots

10, 12, respectively, through which slots the knife blades extend. The knife blades are connected and held a proper distance apart by the insulating spacer bar13. This spacer bar is attached to the knife blade by bolts as and 17. The fuse links connecting the knife blade is designated 19.

The parts hereinbefore just above described are quite usual in renewable knife blade fuses and it is not uncommon to find the spacer bar 13 attached to each knife blade by a pin, as 21, passing through the spacer bar and the narrow inner end of a knife blade.

Usuallya plain nut or plain nut and washer are on the free end of the bolts, as 15, that is, on the lower end thereof, as viewed in Fig. 2. In my construction, however, I have a retaining fastener, as 23 and 25, having a screw-threaded through orifice therein into which the end of a bolt, as 15, may be threaded. This retaining fastener 23 has ample area to bear against the fuse link 19 so that good heat conductivity exists between the retaining fastener 23 and the fuse link 19. In addition the retaining fastener 23 frictionally presses the fuse link 19 into close contact with the face of the narrow inner end of the. knife blade, so that good electrical and thermal conductivity are both obtained. In addition, the retaining fastener, as 23, has, as best shown in Fig. 5, two

fingers

27 and 29. These receive between them a tongue 31 which prevents the retaining fastener 23 when being screwed into place by the turning of a bolt, as 15, from turning with the bolt and deforming or pushing the fuse link out of place. In short, the construction of the retaining fastener 23 is such that in drawing it into place there is no. injuryto the fuse link 19 and a much more efficient thermal and electrical contact is secured between the end of the fuse link and the adjacent metallic electrical and heat conducting parts.

The tongue, as 31, and the similar tongue, as 33, are each a part of a spacer bar receiving saddle, as 35 and 37. This spacer bar receiving saddle is formed with a bottom plate 39 and side pieces, as 41 and 43, so that the ends of a spacer bar are nicely housed in the saddle. Each saddle, in addition, is formed with two depending fingers,

one on each side. One of the depending fingers on saddle 37 at the left hand end of Fig. 2, is designated 45. The two depending fingers on saddle 35, shown at the right hand end of Fig. 3, are designated 47 and 49. The

depending fingers may also be seen in Fig. 5 which shows bore receives a bolt, as 17, so that the bolts, as 15 and t 17, pass through the spacer bar, a saddle, such as 37 or 35, the inner end of a knife blade, as 7 or 55, the fuse link 19 and a retaining fastener as 23 or 25 thereby binding all together tightly.

It will be observed that tongue 33 passes through a slot, as 57, in an inner end of a knife blade, such as 7, as shown at the right hand end of Fig. 2. This slot has one side in the plane of the inner face of an end washer, as 9, and the opposite side of the slot is positioned so that the tongue, as 33, is frictionally and closely positioned therein so that the distance between a bolt, as 15, and the inner face of an end washer, as 9, is always maintained completely uniform.

In the device as shown by Figs. 1 to 5 inclusive, a

tongue, as 33, is shown as a part of a saddle, as 35. I I

may also make the tongue a portion of the retaining fastener. Such construction is shown in Figs. 6 to 8 inclusive. In these views, the tongue is designated 59 and passes through a slot 61 in the inner narrow portion 63 of a knife blade. The tongue 59 is a projection on one end of a retaining fastener 65 which rests against one face of a fuse link 19 and is retained in place by being formed with a through screw-threaded bore 67 adapted for the reception of a screw-threaded bolt, as 69. The screwthreaded bolt, as in the other forms, retains the spacer bar 13, the saddle 71, the knife blade 63, the fuse links 19 and the retainer 65 tightly in place together.

In Figs. 9, l0 and 11 I illustrate a construction in which I employ a retaining fastener 73 like the retaining fastener 65 of Fig. 7, but I also employ a nut 75 on the end of the bolt 77 holding the spacer bar 13 and the link 19 and the other parts firmly together.

As shown by Fig. 11, the bolt 77 may be screw-threaded into the inner narrow end of the knife blade 79 and screw-threaded into the nut 75. However, I may employ an alternative construction as shown in Fig. 12 in which the bolt 81 is screw-threaded into the retaining fastener 83 and into the nut 75, but not into the inner narrow end of a knife blade 85.

Figs. 13 and 14 show another construction in which the spacer bar 13, fuse link 19, knife blade 87 and retain ing fastener 39 are held together by a bolt 91 which is screw-threaded into a through screw-threaded bore 93 and has a flange 95 permanently attached to its upper end as viewed in Figs. 13 and 14.

Figs. 15, 16 and 17 illustrate a construction in which the end washer 97 is provided with projections or nubs, best shown in Fig. 17, and numbered 99, 101, 103 and 105. These nubs closely contact and restrain the tongue 107 of the retaining fastener 109 and also contact closely and restrain spacer bar 13 and the knife blade 111.

An advantage common to all the described forms of the invention is that the respective tongues, insofar as they extend across the slots of the end washers or discs on the inside thereof and in contact therewith, block or seal said slots against the exit of gases and molten metal so as to retard and baflde said exit.

Although I have particularly described a preferred physical embodiment of my invention and modified forms thereof, nevertheless, I desire to have it understood that the forms selected are merely illustrative, but do not exhaust the possible physical embodiments of the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent is:

1. In a renewable fuse having a pair of knife blades, each knife blade having a narrow inner end and a wider outer end, said blades being detachably connected together by both an insulating spacer bar and a fuse link, said bar and link being contained within an insulating housing, end washers for sealing the space be tween the knife blades and said housing, said washers having a central slot to receive the narrow inner portion of the blades so that the washers are disposed between the wide outer portion of the blades and the ends of the spacer bar, and bolts, one passing through each narrow inner end of each blade and the insulating spacer bar, the invention which comprises a through slot formed in the narrow inner end of one of said blades, which slot has one edge in the plane of the inner face of the adjacent end washer, and a metal tongue pass ing through said slot, said tongue bearing on one side against the inner face of the adjacent end washer and on the other opposite side against a side of said slot whereby the end washer and blade are held firmly togather, and a metal body through which one of the.

said bolts extends and of which the tongue forms a part.

2. The device as specified in claim 1 in which the metal body forms a saddle receiving an end of the spacer, bar.

3. The device as specified in claim 1 in which the metal body forms a retaining fastener for an end of the link.

The device as specified in claim 2, in which there is a fiatlink retaining washer screw-threaded onto oneof the said bolts and formed with two fingers, one on each side of a tongue whereby the washer is prevented from turning when the bolt is turned.

5. The device as specified in claim 2 in which the saddle is formed with depending fingers, one on each side each resting against an edge of the inner narrow end of a blade.

6. The device as specified in claim 3 in which there is a saddle receiving an end of the spacer bar and through which one of the said bolts passes.

7. The device as specified in claim 3 in which each bolt is provided with a nut screwed thereon and the metal body is provided with screw-threaded bolt receiving through bore.

8. The device as specified in claim 3 in which the metal body is formed with a through screw-threaded orifice and the bolt is screw-threaded therethrough with the head thereof against the metal body and a fixed flange on the free end of the bolt.

9. The device as specified in claim 3 in which the end washers are provided with inwardly extending inner nubs between which the tongue lies and between which the inner end of a blade and the adjacent end of a spacer bar are positioned in close contact.

10. In a renewable fuse having a pair of knife blades, each knife blade having a narrow inner end and a wider outer end, said blades being detachably connected together by both an insulating spacer bar and a fuse link, said bar and link being contained within an insulating housing, end washers for sealing the space between the knife blades and said housing, said washers having, a central slot to receive the narrow inner portion of the blades so that the washers are disposed between the wide outer portion of the blades and the ends of the spacer bar, and bolts, one passing through each narrow inner end of each blade and the insulating spacer bar, the invention which comprises a through slot formed in the narrow inner end of one of said blades, which slot has one edge in the plane of the inner face of the ad jacent end Washer, and a conductive metal body having a portion formed with a through bore, one of said bolts passing through said bore, said body further having a tongue passing through said last mentioned slot, said tongue bearing against the inner surface of the adjacent end washer and the opposite side of said tongue bearing against a side of said last mentioned slot, and means engaging said bolt and firmly connecting together in fixed spaced relation said blade, said washer, said bolt, said body and said spacer bar, said tongue further extending across said slot of said end washer to baffle the exit of gases from said slot.

11. In a device according to claim 10, said last mentioned means being screw threads formed in said first mentioned portion of said conductive metal body.

References Cited in the file of this patent UNITED STATES PATENTS 1,092,153 Mallory Apr. 7, 1914 1,702,355 McDonald et al Feb. 19, 1929 1,907,739 Clark May 9, 1933 2,198,663 Floten Apr. 30, 1940 2,521,600 Pflaum Sept. 5, 1950 2,556,018 Von Hoorn June 5, 1951