US2253720A - Fuse construction - Google Patents

Description

Aug. 26, 1941. G. F. MCMAHON 2,253,720 A FUSE coNsTRUcTIoN Filed April 12, 1940 2 Sheets-Sheet l 'Aug. 26, 1941. G, F. MCMAHON FUSE CONSTRUCTION Filed April i2, 1940 2 Sheets-Sheet 2 w W7/////////////////////// 5 7/ ,4 V/ y E v a I @ill/5f ,Patented Auges, 1941 UNITED sTATEs PATENT oFFlcE FUSE CONSTRUCTION George F. McMahon,l Chicago, Ill., `assigner to Schweitzer & Conrad, Inc., Chicago, lli., a corporation of Delaware Application April 12, 1940, Serial No. 329,258

15 Claims. (Cl. 20G-120) This invention relates generally to circuit interru'pting apparatus and it has particular relation to fuse links.

An object of this inventionis to secure the insulating tube or sleevev of a fuse link to one of .the link terminals by adhesive means.

Another object of this invention is to provide, asa part of a fuse link, an indicator-which by its absence or presence shows whether or not the fuse link has blown. y

Still another object of this invention is to provide a fuse link witha composite sleeve the lining and sheath of which have different characteristics. l f l A further object of this inventionis to mount a fusible element comprising a tin core and a silver sheath in generally U-shaped -link terminals.

A still further object of this invention is to surround a fusible element comprising a tin core and a silver sheath or tin alone with an arc extinguishing material.

Another object of this invention is to preven loxidation of a tin fusiblev element'surrounded by magnesium borate.

A further object of this invention is to facilitate grasping a terminal of a fuse link for apply. ing it to and removing it from an external terminal.

I constructions hereinafterset forth, the scope of the application ofwhichwill be indicated in the appended claims.

For a more complete understanding of the nature and scope -of this invention, reference may be had to the following detailed description taken in connection with the accompanying drawings, in'which: Y

Figure 1 is a view, in side elevation, f one form of cutout in which the, fuse links-of the present invention may be employed;

Figures 2A and 2B, taken together, constitute a longitudinal sectional view showing the details of construction of the fuse tube that is adapted to -be inserted in the cutout shown in Figure 1;

Figure 3 is a view inside elevation, the fuse tube beingshown iny section,-of a fuse link which 1152A and 2B;

Figure 4 is a view in side elevation, the fuse tube being shown in section, of another form of fuse link; l

Figure 5 is a detail sectional view, at an enlarged scale, taken'along the line 5-5 of Figure 4;

Figure 6 shows another embodiment of the fuse link; and

'Figure' '7 is a detail sectional view, at an enlarged scale, taken along the line 1-1 of Figure 6.

Referring now particularly to Figure 1 of the drawings, it will be observed that the reference character III designates, generally, a cutout which may be mounted on a suitable support such as a crossarm II by means of a suitable clamp I2. A bracket I3 is secured, as shown, to the clamp I2 and is arranged to support a housing I4, which is preferably formed of porcelain. At itsl upper end a handle I5 is provided which may be grasped by the hand of a lineman for removing the fuse tube from the` housing I4.

In Figures 2A and 2B of the drawings the refer-4 louter housing I9, preferably of a phenolic condensation product, such as Bakelite or other thermosetting or thermoplastic material, and a liner 20 formed, for example, of fiber or fibrous'` material impregnated with magnesium borate. At its upper end the fuse tube I8 is provided with a line terminal 2l which is arranged to be con- Il, Figure 1. At its upper end the` terminal 2l is threaded, as indicated at 22, for receiving the handle I5, Figure 1.

Within the fuse tube I8 there is provided a spring and cable assembly that is shown generally at 2l. Thisy assembly comprises a c oil tension spring 25 within whichthere is positioned a flexible conductor or cable 26.' ,'Ihespring 25 and cable 26 are secured at2 their upper ends to a spring and cable fastener 21 which` has a flanged head that rests against the upper end of the terminal 2 i, as shown. The lower endsof the spring 25 and cable 2B are secured to a spring and 'cable fastener 28 which constitute this an external terminal and which has a knurled section 29 to facili- 'tate its being gripped by a suitable tool such as a pair of pliers for application of or removal from a terminal,v shown generally at 30, of a replaceable fuse link, shown generally at 3l. The fuse link 3| is provided with' a'tube or sleeve 32 of insulating material and it has projecting out of its lower end a iexible lead 33 onto which a wedge shaped terminal 34 is deformed for intertting between upstanding ears 35 of a lower line terminal 36 which is mounted at the lower end of the fuse tube I8.

The details of construction of the cutout previously described are generally the same as those illustrated and described in Ramsey Patent No. 2,108,993. It is to the particular details of the construction of the fuse link 3l that the present invention is directed.

In Figure 3 of .the drawings, certain of the novel features embodied in the fuse link construction of the present invention are shown. It will be observed that the fuse tube terminal 30 is generally rod-like in character and therefore that it is relatively infusible. Its upper end portion 38 is threaded for attachment to the spring and cable fastener 28. Just below the threaded portion 38 there is provided a knurled portion 39 for receiving a suitable tool such as a pair of pliers in order to facilitate grasping the terminal 30 for application to or removal from the spring and cable fastener 28.

Immediately below the knurled portion 39 there is provided a generally cylindrical portion 40 to which the tube or sleeve 32 is secured by means of a suitable adhesive 4I. Adhesive material is employed for holding the tube or sleeve 32 in place instead of a pin, as shown in Figures 4 and 6 hereinafter described, in order to reduce the outside diameter of the assembly so that the fuse link can be inserted in a fuse tube having an internal diameter only slightly larger than the outside diameter of the fuse link.

The tube or sleeve 32 is preferably formed of rolled paper impregnated with magnesium borate as disclosed in the copending application of McMahon, Serial No. 266,991, filed April 10,

The lower end portion 42 oi' the terminal 36 is generally tubular in construction and is deformed onto the upper ends of fusible and strain elements 43 and 44. The fusible element 43 may be formed of non-ferrous metal such as silver, copper, aluminum, cadmium, zinc or alloys of these metals, while the strain element 44 is formed of a high strength alloy. such as a nickel chromium alloy. The lower end portions of the fusible and strain elements 43 and 44 are secured by having the upper end portion 45 of a generally rod-like terminal 46 deformed thereon. The lower end of the terminal 46 is generally tubular in character and as indicated at 41 it is deformed onto the upper end of the flexible lead 33. The upper end portion 50 of the wedge-shaped terminal 34 is deformed onto the lower end of the flexible lead 33.

It is desirable that a readily visible indicator be provided for indicating by its absence or presence whether or not the fuse link 3l has blown. For this purpose the wedge-shaped terminal 34 is provided with a generally tubular section I which is deformed, as indicated at 52, onto` the upper end of an elongated insulator member 53 which constitutes an indicator member. 'I'he member 53 is, preferably formed of a white moulded plastic so that it will be readily visible from the ground. As shown in Figure l, theindicator member 53 projects a substantial distance below the lower end of the housing I4 so that it is readily visible. At its iower end the indicator member 53 is provided with grooves 54 for receiving a pull-up string for facilitating the re-fusing of the fuse tube I8.

In operation, when the fusible and strain elements 43 and 44 of the fuse link 3I blow, the spring 25.is no longer restrained. Accordingly, it retracts the upper fuse link terminal 30 and tube or sleeve 32 secured thereto into the tube I8, thereby elongating the arc formed between ythe relatively infusible terminals 30 and 46 for extinguishing the same. Due to the heat of the arc thus formed, water may be evolved from the inner surface of the tube or sleeve 32 and it further assists in extinguishing the arc. Since the lower fuse link vterminal 46 is no longer restrainedy it and the indicator member 53 drop out or are blown out of their normal positions at the lower end of the tube I8. It will thus be apparent that the presence of the indicator member 53 at the lower end of the housing I4 shows that the fuse link 3| has not blown. However, its absence indicates that it has blown and that the cutout should be re-fused.

In Figure 4 of the drawings, another embodiment of the fuse link construction is shown generally at 51. The link 51 is provided with an upper relatively infusible terminal that is shown, generally, at 58. Its upper end portion is threaded as indicated at 59 for attachment to the spring and cable fastener 28, Figure 2B, or for receiving a flanged tting 60 for mounting in other types of cutouts, such as an expulsion type of cutout. Below the threaded portion 59 there is provided a knurled portion 6I for facilitating the securing of the .terminal 58 in position or removing it therefrom, as previously described.

Below the knurled portion 6I there is provided a longitudinally knurled portion 62 over which a composite tube or sleeve, shown generally at 63, is positioned. This composite sleeve 63'may be secured to lthe terminal 58 by means of a transversely extending pin or screw 64.

The composite sleeve 63 preferably comprises a liner 65 formed of rolled paper impregnated with magnesium borate and an outer sheath 66 formed of fiber. The magnesium borate in the li-ner 65 evolves a considerable amount of water i vapor under the heat of an arc for assisting in extinguishing it while the fiber sheath 66 serves to reinforce the liner 65 and protects the same in handling. y The ber sheath 66 also possesses arc extinguishing properties but to a lesser degree than magnesium borate.

The lower portion 68 of the upper fuse link terminal 58 is of al tubular construction and is deformed onto the upper end of a strain element 69 which, as previously indicated, may be formed of a nickel alloy wire. In deforming the lower portion 68 of the terminal 58, a generally U- shaped fusible element receiving portion is formed and in this, one end of a fusible element, sho'vs'm generally at 10, is soldered, as indicated at 4 As shown in Figure 5 of the drawings, the fusible element 16 comprises a core 12, formed principally of tin, and a sheath 13, formed principally of silver. The silver-tin fusible element is more fully described in the copending application of Triplett, Serial No. 144,789, filed May 26,

in construction and it is deformed onto the lower end of the strain element 69 for fastening thereto. In deforming the portion 14 a generally U- shaped fusible element receiving portion is provided, as described in the portion 68 and in it the lower end of the fusible element 10 is positioned and secured in place by solder 16.

The generally U-shapedportions 68 and 14 of the fuse link terminals 58 and 15 form a cradle constructiomwhich isv described in more detail in Triplett et a1. Patent No; 2,174,767.

The lower fuse link terminal 15 is deformed onto one end of a flexible lead 11 which extends "cured to the corresponding terminal, as will be readily understood.

In Figure 6 of the drawings, the fuse link shown generally at 80 -ls generally similar lin construction to the fuse link 51, shown in Figure 4, and described hereinbefore. However, in the fuse link 88 the fusible element,.shown generally at 8|, is composed of non-ferrous metal such as copper, cadmium, aluminum, zinc or alloys of the same, as indicated at 82 in Figure 7 of the drawings.

With a view to preventing oxidation of the tin core 82, or of other cores consisting of readily oxidizable metals, the core is provided with a baked enamel sheath 83 which is capable of withstanding without injury theh'eat generated by the core 82 substantially up to or just below its melting point. Preferably, the enamel sheath83 is formed by spraying on the tin core 82 after it has been assembled in the terminals 58 and 15 a1 lacquer which can be obtained in theI open market under the trade name of Duranite.

' After the spraying operation has been completed,

the assembly is placed in an oven and baked at 250 F. to 275 F. for about one hour in order to harden and polymerize the resin in the lacquer. f Fuse links of the .type herein disclosed are particularly well adapted to clear low current faults at low power factor and high recovery voltage. It has been found that operationunder these conditions using the present invention is superior to results obtained when other materials such as liber are used.

Since certain further changes may be made in the foregoing constructions and different embodiments of the invention can be imade without departing from the scope thereof, it vis intended that allv matter 'shown in the accompanying drawings and described hereinbefore shall befiniterpreted as illustrative and not in a limiting sense. A

What is claimed as new is:

1. In a fuse, in combination, a pair of terminal means and fusible means` interconnecting the same, one of said terminal means being rod-likel in character and adapted to be connected to an external terminal at one end and to said fusible means at the other end, a sleeve-of insulating material containing magnesium borate telescopically related to said pair of terminal means, and

2. A fuse linkV comprising, in combination, a

pair of terminal means adapted to be connected to line terminals and interconnected by fusible means, an elongated insulator member acting as an indicator, and a sleeve vconstituting an extension of one of said terminal means and deformed onto one end of said elongated insulator.

3. In a fuse, in combination, a pair of spaced relatively infusible' terminals, fusible means interconnecting said terminals, and va. composite insulating sleeve surrounding'said fusible means having a sheath formed of are extinguishing material and a liner closely fitting therewith and carrying magnesium borate.

4. In a fuse, in combination, a pair of `spaced relatively infusible terminals, fusible means interconnecting said terminals, and a composite insulating sleeve surrounding said fusible means having a fiber sheath and a -liner extending throughout its entire length and carrying magnesium borate.

5. In a fuse, in combination, a. pair ofspaced" relatively infusible terminals, fusible means interconnecting said terminals, a composite insulating sleeve telescopically related to said terminals and having a fiber sheath and a liner c arrying magnesium borate, and means for securing said composite sleeve to at ,least one of said terminals.

6. In a fuse, in combination, a pairv of spaced relatively infusible terminals, fusible means interconnecting said terminals, a composite insulating sleeve telescopically related to said terminals and having a ber sheath and a liner carrying magnesium borate, and means for securing said composite sleeve Ito one of said terminals, the other terminal being free to move out of said sleeve on blowing of said fusible means.

7, In a fuse, in combination, a pair of terminal members having end portions extending toward each other, said end portions having laterally opening aligned U-shaped fusible element receiving portions, strain means interconnecting said terminal members, a fusible element comprising a tin core and a silver sheath secured tubular end portions;- said tubular end portions' being -deformed in such manner as to form substantially U-shaped fusible element receiving portions, a fusible element comprising a tin core and a silver sheath also interconnecting said terminals with its ends disposed in said U- shaped fusible element receiving portions, and a sleeve of insulating material secured to at least one of said'terminals and surrounding said fusible element and carrying magnesium bor-ate in such position that it is exposed Yto the heat of the arc formed on blowing of said fusible element.

9. In a fuse, in combination, a pair of spaced relatively infusible terminals, la fusible element interconnecting said terminals comprising a core composed principally of tin and a sheath composed principally of silver; and a sleeve of insulating material carrying magnesium boratel surrounding said fusible element.

10. In a fuse,in combination, a pair of spaced relatively infusible terminals, a fusible element interconnecting said terminals comprising a core composed principally of tin and a sheath composed principally oi' silver, and a sleeve of ce1- lulosic material impregnated with magnesium borate surrounding said fusible element.

11. In a fuse, in combination, a pair of spaced relatively infusible terminals, a fusible element interconnecting said terminals comprising a core composed principally of ltin and a sheath composed principally of silver, and a rolled paper sleeve impregnated with magnesium borate surrounding said fusible element.

12, In a fuse, in combination, a pair of spaced relatively infuslble terminals, a fusible element selected from the class consisting of tin, copper, aluminum, cadmium and zinc interconnecting said terminals, and a sleeve of insulating material carrying magnesium borate surrounding said fusible element.

13. In a fuse, in combination, a pair of spaced relatively infusible terminals, a fusible element selected from the class consisting of tin, copper, aluminum, cadmium and zinc interconnecting said terminals, anda sleeve'of cellulosic mate- :rial impregnated with magnesium bor-ate surrounding said fusible element.

14. In a fuse, in combination, a pair of spaced relatively infusrlble terminals, a fusible element selected from fthe class consisting of tin, copper, aluminum, cadmium and zinc interconnecting said terminals, and a rolled paper sleeve impregnated with magnesium Aborate surrounding said fusible element.

15. In a fuse, in combination, a pair of spaced relatively infusible terminals, a fusible element composed o1' an oxidizable metal interconnecting said terminals, an enamel coating on said fusible element to prevent oxidation thereof, and a sleeve of insulating material carrying magnesium borate surrounding said fusible element.

GEORGE F. MCM'AHON.

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