US2047365A - Fuse switch - Google Patents

Description

July 14, 1936. c. A. FOX 2,047,365

FUSE SWITCH Filed May 20, 1935 2 Sheets-Sheet l ATTOBN'Y July 14, 1936.

LEW.

Filed May 20, 1935 C. A. FOX

FUSE SWITCH 2 Sheets-Sheet 2 Wis) huavrae OMB; 5 Afl/h' fax ATTORNEY Patented July 14, 1936 UNITED STATES PATEN'T. OFFICE FUSE swrrcn Charles Adin Fox, St. Louis, Mo., assignor to James R. Kearney Corporation, St. Louis, Mo., a corporation of Missouri Application May 20, 1935, Serial No. 22,408

.17 Claims. (01. 200-122) This invention relates generally to fuse switches, and more specifically to an improved fuse switch which, in addition to affording protection against short circuit faults in an electrical circuit with which the fuse switch is associated, serves also, because of certain thermal means forming a part of the fuse switch, to afford maximum protection against overload faults in the circuit, the predominant object of the invention being to provide an improved fuse switch of this type which is capable of performing its intended function in a highly efllcient manner.

It is quite generally known to persons familiar with such matters that for a number of years it has been the practice to protect distribution transformers of electrical systems through the use of fuse switches of various types. These fuse switches generally depend on opening the circuit by melting portions of the fuse elements, or by melting soldered joints which hold parts of the fuse elements together. The melting of the fuse elements or the joints thereof takes place at certain predetermined current values and is dependent on the size and length of the fuse elements, the kind of wire thereof, and the melting point of the wire constituting the fuse elements or the solder thereof. Owing to the fact that a fuse element is necessarily small, the temperature rise of the element follows very closely the current rise in the circuit. The lag of the temperature curve of the fuse element behind the current curve of the circuit can be varied to some extent by changing the physical dimensions of the material, but essentially the.fuse remains a quick operating unit.

This characteristic makes the fuse ideal for short circuit protection (high current value faults), but naturally prevents it from having the necessary characteristics for overload protection. In order to prevent needless service interruptions from temporary overloads it is necessary, and has become general practice, to use a fuse element from two to five times the actual capacity of the transformer. With the natural increase in the use of electric service and the ever increasing number of electrical devices used, the load on the normal transformer is slowly creeping upward until finally the original excess capacity will have been exceeded, and unless there has been considerable time spent in load checking or considerable outlay put in excess transformer capacity, or both, transformer loss is inevitable.

The improved device disclosed herein, which may be described as a thermo-relay fuse switch, comprises a cartridge mechanism which may be inserted in a standard switch mounting. It preserves the high quality short circuit protection of the fuse now in general use, and adds to this the ability to afford overload protection which the present fuse does not do. This combination 5 enables the excess transformer capacity to be reduced to a minimum, and also provides for the reduction to the minimum of the load survey cost.

Briefly stated, overload protection in the im- 10 proved device is obtained by arranging a small heating element in series with the fuse element and. interposing heat-insulating material between the heating element and a thermo-tripping element. The temperature of the thermo-trip- 15 ping element can be made to lag behind the current flow in the heating element suiiiciently long to care for all temporary load demands without interrupting the circuit by having the excess heat absorbed by adjacent parts of the switch struc- 20 ture, thus keeping the temperature of the thermo tripping element below the tripping point. In the event, however, of the overload proving permanent, the temperature of the thermo-tripping element will continue to rise until the switch is 5 tripped out, thus protecting the transformer from injury caused by continued overload. The lag of the temperature of the thermo-tripping element behind the load current is controlled by the amount and character of the heat-insulating meso dium between the heating element and the thermo element, and somewhat by the construction of the assembly.

Fig. 1 is a side elevation of the improved fuse switch, parts of the switch mounting being broken 35 away to conserve space. j

Fig. 2 is an enlarged section on line 2-2 of Fig. 1, witha part of the housing of the heating element broken away in order to show inner parts thereof.

Fig. 3 is a front elevation of the cartridge of the improved fuse switch.

Fig. 4 is an enlarged, fragmentary view, partly in vertical section and partly in elevation, of the lower portion of the cartridge of the improved structure.

Fig. 5 is a vertical section on line 55 of Fig. 4.

Fig. 6 is a fragmentary, inverted, plan view of the cartridge as illustrated in Fig. 4.

Fig. 7 is a fragmentary, side elevation of the lower portion of the cartridge showing said portion as it appears when the theme-tripping element has been actuated and dropping-out movement of the cartridge has started. 55

In the drawings, wherein is shown for the purpose of illustration, merely, one embodiment of the invention, A designates a standard switch mounting which includes an insulator B, upper and lower line terminals C and D secured to said insulator, upper and lower contact members E and F, and a bracket G by which the switch mounting is secured to a cross-arm or other element (not shown) by which it is supported. For the purpose of this disclosure, the upper contact member E may be considered to comprise a length of heavy wire fixed to the upper terminal and bent to provide a pair of substantially parallel, forwardly extended leg portions between which a portion of the cartridge of the improved structure is interposed for the purpose of providing mechanical and electrical connection between the cartridge and said upper contact member. The lower contact member F may be considered to comprise a forwardly extended member fixed to the lower terminal D and provided with laterally extended elements H which serve as hinge members for the cartridge of the improved structure.

Referring now to the cartridge of the improved fuse switch, I designates an expulsion tube formed of suitable insulating material or combinations of insulating materials. At its upper end the tube I is provided with a cap 2, which is in the form of a sleeve that embraces the upper end portion of the tube, said cap being pinned or otherwise secured to the tube and being provided with an upstanding finger 3 which is interposed between and is frictionally gripped by the outwardly extended, parallel legs of the upper contact member E when the cartridge is in the fusing position, for the purpose of mechanically and electrically connecting the upper end of the cartridge to the upper contact member E. At the top of the cap 2 an opening is provided which receives a head element 4 associated with a fuse element 5, said head element being seated against a face which surrounds the opening at the top of the cap 2 and having a portion 4' which extends a short distance downwardly into the tube I. The fuse element is attached to the head element 3 and is extended downwardly therefrom through the tube I in the usual manner. Also, the cap 2 is provided with a ring 6 which facilitates manual movement of the cartridge into and out of the fusing position with the aid of an insulated switch stick or fuse puller.

Fixed to the tube I of the cartridge at a point spaced upwardly ,from the lower end thereof is an arm I, which includes a rearwardly extended portion I and a downwardly extended portion 8 provided at its opposite sides with car portions 9. The rearwardly extended portion l and the downwardly extended portion 8 of the arm are preferably, though not necessarily, of substantially U-shaped cross-sectiomas shown in Fig. 2, and said arm I includes a collar portion It which fix edly embraces the tube I of the cartridge.

Pivotally connected to the arm I is a hinge element I I, said pivotal connection between the arm and the hinge element being accomplished through the use of a pivot pin I2 which is extended transversely of the arm and the hinge element through apertures in the ear portions 9 of the arm and in portions I3 of the hinge element which are disposed between said ear portions (see Fig. 2). The hinge element I I comprises spaced apart side portions I I which are integrally connected by web portions II to provide a unitary structure, and also said hinge element includes an in- 7 tegrally formed, substantially circular plate porment I I are provided also with hook portions I6 10 located above the hook portions I5, which are adapted to be engaged by an insulated switch stick when it is desired to detach the assembly comprised of the cartridge and the hinge element II from the switch mounting.

Fixedly supported by the plate portion I 4 of the hinge element I I is a thermal unit H, which includes a tubular member I8 (Figs. 4 and 5). The tubularelement I8 extends upwardly from the plate portion I4, as shown most clearly in Figs. 20

a and 5, and said tubular elementis surrounded in spaced relation relative thereto by a casing I9 of suitable insulating material. In the particular embodiment of the invention illustrated in the drawings, the casing I9 is circular in hori- 3| zontal section and is seated at its lower end in an annular recess 20 formed in the plate portion II at the outer edge thereof. At the top of the casing I9 the thermal unit Ill includes a cap 2! which includes an upstanding, hollow portion 22 and an annular flange portion 23, the lower face of said flange portion being in contact with the top edge of the casing l9, and said flange portion being provided with an annular, downwardly extended portion 24 which embraces the upper portion of the casing, as shown in Figs. 4 and 5, so as to maintain the casing in its proper position relative to the cap 2|.

1 At the upper end of the tubular member I8 a head 25 is provided which is recessed at its outer edge, as indicated at 26. The upper wall of the recess 26 is seated in contact with the top edge of the tubular member l8, and the lower portion of the head within the recess 26 is extended downwardly into the upper portion of the tubular memher a. short distance. .Arranged immediately beneath the head 25 is a rod 27 which is fixedly seated at its opposite ends in alined apertures formed in the wall of the tubular member I8 and extends transversely through the hollow interior of the tubular member. The rod 27 has arranged in contact with its lower surface portion a more or less "I'- shaped element 28 which is provided with a depression or seat 28', the face of which contacts with the lower face of the rod. The upper, substantially horizontal portion of the T-shaped element 28 is provided with a pair of screw-threaded openings formed therethrough, through which adjusting screws 29 are extended, these adjusting screws passing also through alined apertures formed through the head 25. To the downwardly extended leg of the T-shaped element 28 a thermo-tripping element 30 is fixedly attached by means of suitable fastening means 30', said thermo-tripping element being provided at its lower .1

end with a more or less hook-shaped portion 3|. The cap 2| at the upper end of the thermal unit I I is secured to the head25 located at the top of tubular member I8 by a screw 32, which is extended through an opening formed through the top wall of the cap and is screwed into a screwthreaded opening formed in the head.

Pivotally attached-to spaced apart extensions 33 of the hinge element I I (see Figs. 4 and 6) is a member 34 which includes a body portion 35 through which a'pivotpin 3G is extended, said pivot pin being extended also through apertures formed through said spaced extensions 33. The member 34 includes a shaft 31 which is extended outwardly from the body portion 35, and this shaft rotatably supports a circumferentially grooved pulley 31' formed of insulating material about which, as will presently appear, the fuse element of the fuse switch passes. Extended upwardly and rearwardly from the body portion 35 of the member 34 is an extension 38, which is l provided at its free end with a nose portion 39 having a' flat underface 39', this flat face being adapted to be engaged by a flat face 40 at the outer end of the hook-shaped portion 3| of the thermo-tripping element 30 as shown most clearly in Fig. 4. I

Arranged to surround the tubular member I8 of the thermal unit I1 is an elongated sleeve 4! formed of material characterized by the ability to act as a heat insulator as well as an electrical insulator. The sleeve 4| insulates from the tubular member I8 an electric heating coil 42, this heating coil being interposed between the sleeve 4| and the casing l9, whichfas already stated herein, is formed of suitable electrical in sulating material, fiber, for instance. One end of the wire which produces the heating coil 42 is attached, as shown most clearly in Fig. 2, to a connector 43 by means of a suitable fastening device 44, and the opposite end of said coilproducing wire is attached directly to the web portion li of thehinge element H by means of a suitable fastening device 45, as shown in Fig. 4. The connector 43 includes an outstanding, screw-threaded shank 46 (Figs. 1, 2, 3, and 7) at the base of which a disk 41 is located, and mounted on this shank is a wing-nut 48 which has a washer 49 associated with-it. As is shown most clearly in Fig. 2, the fuse element 5 is electrically connected to the connector 43 by having a portion thereof turned about the shank portion 46 and clamped between the washer 49 and the disk 41.

When the cartridge is disposed in the fusin position, the fuse element 5 is held under constant tension, this by reason of the tendency of the hinge element II to turn about the pivot l2 resulting from forces set up by downward pressure exerted against the cartridge by the resilient upper contact E. When the fuse element becomes ruptured upon the commence of a short circuit, the hinge element l I, freed at its outer or fuse element engaging end and acting under the forces imparted thereto, turns rapidly about the two axes defined by the hinge members H and the pivot l2. Movement of the hinge element ll about the hinge member H is accompanied by endwise lowering of the cartridge tube, which,

when clear of the upper contact E, swings under action of gravity outwardly and downwardly to the full open position. It will appear that the hinge element I I considered as a lever has a high velocity ratio and that its outer or fuse element engaging end moves very rapidly. Accordingly the ruptured ends'of the fuse element become element 30 frees the nose portion of the extension 38 of the member 34, thereby permitting the tensioned fuse element to move said member 34 about its pivot 36, the extension 38 swinging rearwardly and downwardly beneath'the rearwardly displaced lower end of the thermo-tripping element and the pulley 31 moving with said extension to a tipped up position, where the fuse element may slip from the circumferential groove of said pulley, as shown by dotted lines in Fig. '7. This frees the fuse element engaging end of the hinge element I I and permits said hinge element to turn rapidly about the two axes defined by the hinge members H and the pivot l2 so as to cause the cartridge to drop out of the fusing position, as already explained.

As heretofore explained-herein, the temperature'of the thermo-tripping element 30 is caused to lag behind the current flow in the heating element, so as to care for all temporary load demands without interrupting the circuit. This is accomplished by the use of the insulating sleeve 4| which is interposed between the thermo-tripping element and the heating coil 42. Therefore the heat produced by the heating coil, because of ordinary load demands on the circuit, is not sufficient to heat the thermo-tripping element to the tripping point because of the presence of the insulating sleeve. However, if an overloadbecomes permanent the temperature of the thermotripping element rises to the point where the thermo-tripping element is actuated and the cartridge immediately drops out of the fusing position, as described.

It is important to note that the thermo-tripping element 30 may be adjusted by manipulating the screws 29 so as to move the T-shaped element 28 in a rocking or pivotal manner relative to the rod 21. Thus the lower hook-shaped end of said thermo-tripping element may be po-' sitioned with respect to the nose portion 39 of ducing means for releasing said cartridge for displacement from'the fusing position by applying heat to said element of said cartridge-maintaining means. i

2. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be. releasably supported by the switch mounting, means including a thermo-tripping element for maintaining said fuse cartridge in the fusing position, and means for releasing said cartridge for displacement from the fusing position, the last-mentioned means including an electrical heating element adapted to influence said .thermo-tripping element.

3. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting, a fuse eley from .the fusing position,

means for releasing said cartridge for displacement from the fusing position, said means including an electrical heating element arranged in series with said fuse element and adapted to impart heat to said theme-tripping element.

4. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting, a fuse element associated with said fuse-cartridge, means including a thermo-tripping element for maintaining said cartridge in the fusing position, means for releasing said cartridge for displacement said means including an electrical heating element arranged in series with said fuse element and adapted to impart heat to said theme-tripping element, and means for controlling passage of heat from said heating element to said thermo-tripping element.

5. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting, a fuse element associated with said fuse cartridge, means including a thermo-tripping element for maintaining said cartridge in the fusing position, means for releasing said cartridge for displacement from the fusing position, said means including an electrical heating element arranged in series with said fuse element and adapted to impart heat to said thermo-tripping element, and insulating means for controlling passage of heat from said heating element to said thermo-tripping element.

6. ,A fuse switchcomprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting in the fusing position, a hinge element movably connected to said switch mounting and to said fuse cartridge and movable to release the fuse cartridge for displacement from the fusing position, heat-responsive means for maintaining said hinge element in position where the fuse cartridge is in the fusing position, and electrical heating means for causing said heat-responsive means to release said hinge element and permit the fuse cartridge to be displaced from the fusing position.

7. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting in the fusing position, a hinge element pivotally connected to said switch mounting and to said fuse cartridge and movable to release the fuse cartridge for displacement from the fusing position, heat-responsive means for maintaining said hinge element in position where the fuse cartridge is in the fusing position, and electrical heating means for causing said heat-responsive means to release said hinge element and permit the fuse cartridge to be displaced from the fusing position.

8. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting in the fusing position, a hinge element pivotallyconnected to said switch mounting and to said fuse cartridge and movable to release the fuse cartridge for displacement from the fusing position, heat-responsive means comprising a thermo-tripping element for maintaining said hinge element in position where the fuse cartridge is in the fusing position, and electrical heating means for causing said heatresponsive means to release said hinge element and permit the fuse cartridge to be displaced from the fusing position.

enemas movable to release the fuse cartridge for displace-- ment from the fusing position, heat-responsive means comprising a thermo-tripping element for maintaining said hinge element in position where the fuse cartridge is in the fusing position, and

electrical heating means for causing said heatresponsive means to release. said hinge element and permit the fuse cartridge to be displaced from the fusing p sition, said thermo-trlpping element and said electrical heating means being carried by said hinge element.

10. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting in the fusing position, a fuse element associated with said fuse cartridge, a hinge element pivotally connected to said switch mounting and to said fuse cartridge and movable to release the fuse cartridge for displacement from the fusing position, said hinge element being engaged by said fuse element, heat-responsive means for maintaining said hinge element in position where the fuse cartridge is in the fusing position, and electrical heating means for causing said heat-responsive means to release said hinge element from said fuse element and permit the fuse cartridge to be displaced from the fusing position.

11. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting in the fusing position, a fuse element associated with said fuse cartridge, 'a hinge element pivotally connected to said switch mounting and to said fuse cartridge and movable to release the fuse cartridge for displacement from the fusing position, said hinge element being engaged by said fuse element, heatresponsive means for maintaining said hinge element in position where the fuse cartridge is in the fusing position, and electrical heating means arranged in series with said fuse element for causing said heat-responsive means to release said hinge element from said fuse element and permit the fuse cartridge to be displaced from the'fusing position.

12. A fuse switch comprising a switch mounting, a fuse cartridge adapted to be releasably supported by the switch mounting in a fusing position, a fuse element associated with said fuse cartridge, a hinge element pivotally connected to said switch mounting and to said fuse cartridge and movable to release the fuse cartridge for displacement from the fusing position, movable means carried by said hinge means and engaged by said fuse element, heat-responsive means for engaging'said movable means and maintaining said hinge element in position where the fuse cartridge is in the fusing position, and electrical heating means for causing said heat-responsive means to release said movable means for movement so as to permit the fuse element to be disengaged therefrom and permit the hinge element to move to displace the fuse cartridge from the fusing position.

13. A fuse cartridge provided with a fuse element and adapted to be releasably supported by a switch mounting, movable means associated with said fuse cartridge and engaged by the fuse ele ment thereof and operable to release the fuse cartridge from the fusing position, restraining means oatmeal lot aeitl movable Zoe movement oi eaiel movable rneane, anti electrical heating means arranged to influence Enid restraining means in a manner to release mov able means for movement.

14. A fuse cartridge provided with inee element and adapted to be reieeeablv supported my a switch mounting, movable means eeeociateti it tn said iuse cartridge anal engaged by the fuse element thereof anti operable to release the time cartridge from the fusing position, restzcaining means carried Toy eairl movable means for restraining movement oi said movable means, and electrical heating means cerrleti by said movable means and arranged to influence eaiei restraining means in a manner to release said. niovaioie means tor movement.

15. A time eartrltlee provided a lane element and adapted to be releasaloiv snpnortetl "my a switch mounting, movalole means aeeooiatezl with said Knee cartridge and eneaeerl by the fuse element thereof and operable to release the iuee cartridge from the fusing position, reetrainin g means comprising a thermo-ti'll i ing element earrieel by said movable means for restraining move ment of saici movable means, anti eleetrieal heating means arrangexi to influence sale means in a er to release movable meane lot movement,

iii. A Knee eai'tnolge provided ele ment anti adenteol ,to be ieleaeablv supported lay a switch mounting, movable meane aesoeiatezl with eaiel iuee oartrirlge and engaged by the time element thereof and operable to release the time eartridge from the fusing position, resting me comprising a merino-tripping element carried by said movable means for restraining movement of said movable means, electrical heating meant aeinngeti to influence said restraining means in a manner to release saiol movable means for-move ment, and means for manually adjusting the position of saicl theme-tripping element.

17. A fuee cartridge proviclezl with a ins e element and adapted to be ieleasalolv supported in? a ewitcii mounting, movable means associated with said fuse cartridge and engaged in? the i'uee ele ment therecri and operable to release the fuse cartrlolge from the fusing position, restraining mean-a comprising a thermo-tripping element oat'rietl lay eaiel movable means for rwtrainine movement oi said movable means, electrical heating means ar ranged to influence saiel restraining means in a manner to release said movable means ifot move ment, and means incline adjusting screws tor manually adjusting the position of said then-motripning element.

annt WK.

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