US3048680A - Fuse cutout - Google Patents

Description

Aug. 7, 1962 G. R. MCCLOUD 3,048,680

FUSE CUTOUT Filed Oct. 7, 1960 INVENTOR. 650965 E. M: 6201/0 BY Patented Aug. 7, 1962.

3,048,680 FUSE CUTOUT George R. McCloud, South Milwaukee, Wis., assignor to McGraw-Edison Company, Milwaukee, Wis., 21 corporation of Delaware Filed Oct. 7, 1960, Ser. No. 61,187 9 Claims. (Cl. 200-114) This invention relates generally to fuse cutouts and more particularly to an open type cutout construction which experiences no contact burning or arcing during high fault current interruption.

Conventional fuse cutouts employ a gas evolving fuse tube or a gas evolving fibre liner within a fuse tube and a rupturable fuse link or current responsive element within the fuse tube for electrically bridging a pair of spaced contacts. In interrupting fault currents the fuse link ruptures, an arc is drawn which raises the temperature in the fuse tube, and gases are resultantly evolved from the tube or liner which serve to extinguish the arc.

Due to the fact that gases are evolved at an extremely rapid rate within the limited confines of the fuse tube they, the gases, develop a relatively high pressure. In order that this pressure does not serve to burst the fuse tube provisions must be made to vent the gases from the fuse tube. Generally this is accomplished by leaving the lower end of the fuse tube open and by enclosing the other end of the fuse tube with a cap. In some cutouts this cap is designed to rupture above a certain internal tube pressure, thusly providing a second vent opening to help relieve high gas pressures within the fuse tube.

The rapid escape of gases from the fuse tube sets up an oppositely directed jet type thrust force which serves to move the fuse tube either axially or about a predetermined pivot point.

In addition to the above movement considerable bouncing of the fuseholder also takes place during current interruption. This movement in the fuseholder tends quite frequently to either momentarily or permanently separate the stationary and movable contacts of the cutout prior to complete arc extinction; a condition which leads to burning and pitting of the contacts and/ or associated parts of the cutout due to arcing therebetween. This tendency is generally more pronounced at the upper contacts than at the lower contacts but can occur at either or both of the contacts depending on the particular details of various cutout designs.

Throughout the remainder of the specification fuseholder is intended to mean an assembly of a fuse tube(s), together with the parts necessary to enclose and provide means of making contact with the current responsive element and the stationary contacts while fuse tube is intended to mean a tube of insulating material which encloses the conducting element.

Prior art devices have attempted to compensate for this fuseholder movement by utilizing stationary spring contacts or spring biased contacts. This approach has not been completely successful since the springs or spring contacts do not always follow the fuse tube contact (movable) quickly enough to maintain contact therebetween. Hence burning and pitting of the contacts quite frequently occurred. In addition to these disadvantages follow spring members are costly and are generally very prone to corrosion.

It is therefore an object of this invention to provide a fuse cutout wherein burning and pitting of the contacts during fault current interruptions are eliminated.

Another object of this invention is to provide a fuse cutout wherein separation of the contacts is positively prevented until the are within the fuse tube has been extinguished.

A further object of this invention is to provide a fuse cutout having a fuseholder locking mechanism which will maintain contact pressure until after the fuse link is expelled from the fuse tube.

A still further object of this invention is to provide a fuse cutout having an upper contact assembly which coacts with a fuseholder locking mechanism to prevent accidental removal of the fuseholder from circuit bridging position until after the circuit has been interrupted.

Other objects and advantages of my invention will be apparent from the following description of the preferred embodiments of the invention taken in connection with the accompanying drawings in which:

FIG. 1 is a partially cut away view in elevation of a fuse cutout embodying the invention;

FIG. 2 is a plan view of the device of FIG. 1 taken along the line 2-2 of FIG. 1; and

FIG. 3 is an exploded perspective view of portions of the fuse cutout embodying the invention.

Referring now to FIGS. 1 and 2, 10 indicates generally an open type expulsion fuse cutout having an insulator 12, an upper contact assembly 13, a lower fuseholder support 14 aflixed to the insulator 12, a lower contact assembly 15 and a fuseholder 16 comprising, a gas evolving fuse tube 16' having a rupturable fuse link 17 (or other current responsive element) therein electrically bridging the upper and lower stationary contacts and upper and lower contacts 25 and 32 respectively.

The upper stationary contact assembly 13 is affixed to insulator 12 by fastening member 18 and comprises a supporting hood 19, a U-shaped contact 20 affixed to the hood 19 and a U-shaped leaf spring 21 overlaying the contact 20 and also affixed to the hood 19. The leaf spring 21 serves to inwardly bias the contact 20. While the spring and contact are shown as being affixed to the hood it is within the scope of this invention to afiix the spring and contact to the insulator directly or indirectly and to eliminate the hood altogether. It is also conceivable and within the scope of this invention to unify the functions of the leaf spring 21 and contact 20 in a single member which may be of beryllium copper, Phosphor bronze or the like.

A stationary latching lug 22 is affixed to the supporting hood 19 and extends below the spring and contact and away from the insulator 12.

On the upper portion of the fuse tube 16' is affixed a ferrule member 23 which has a thru bore and which is enclosed at its upper end by closure means 24 which may or may not be rupturable depending on the fuse cutout duty. Two offset cam-like projecting contact portions 25 extend outwardly from ferrule member 23 and are adapted to engage both of the inner sides of the contact 20. Thus the effect of the pressure exerted by spring member 21 thru contact 20 on member 23 is to impart a counterclockwise rotational moment to the fuse tube 16' and affixed member 23. (Relative to FIG. 2.) The outer ends 20' of contact 20 are flared outwardly so as to facilitate the initial engageability of portions 25 and contact 20. Pivotally attached to member 23 is a pull ring 26 and projecting latch 27 which is engageable with stationary lug 22 to provide a positive locking mechanism. The pull ring and latch are so interconnected that downward movement on the pull ring effects upward movement of the latch which disengages the latch from the latching lug 22. In this connection it should also be noted that counter clockwise rotation of the fuse tube '16 and member 23 serves to disengage the latch 27 from latching lug 22.

Surrounding the lower end of the fuse tube 16' and firmly attached thereto is an inner sleeve member 28 (FIGURE 3) which has two opposed projecting lugs 29 protruding therefrom. The lugs 29 may be provided with internal screw threads 29 so that a screw 40 may be aoaseso inserted therein to firmly attach sleeve or collar 28 to the fuse tube 16'. The lower end of the sleeve or collar 28 has an intergal arm portion '38 which extends in a plane at substantially right angles to the fuse tube axis and normally toward the insulator "12. A roller member 31 having a smooth bearing surface is aflixed to the end of arm 30 and extends in the general horizontal plane of the arm.

An outer sleeve contact member 32 surrounds the sleeve 28 and has opposed transversely extending slots 33 therein which are adapted to receive projecting lugs 29 on sleeve 23. The reception of lugs 29 in slots 33 serves to support the outer sleeve 32 while allowing relative torsional movement between the inner sleeve 28 (fuse tube) and the outer sleeve 32.

The lower side of outer sleeve 32 has half moon trunnion members 34 extending therefrom and a pivot pin 35 which extends through the trunnion members. On one side of contact sleeve 32 is afiixed a fuse link anchoring member 32' which serves to anchor one end of fuse link 17 to the sleeve 32. A link flip lever 36 and biasing spring 36 are mounted on the pivot pin 35 between the trunnions 34 in such a manner that the lever is ordinarily biased in a clockwise direction relative to FIG. 3. The lever 36 has leg portions 37 and a transverse portion 38. The lever is so constructed that when transverse portion 38 is touching or in close proximity to the lower end of the fuse tube 16' and engaging fuse link 17 (FIG. 1) that the only tensile force exterted on the link is essentially that exerted by spring 36. It may thusly be seen that link tension is therefore independent of contact pressures.

Attached to fuseholder support 14 as by fastening means 39 is bearing member 41 which is adapted to receive trunnion members 34 and thusly provide a pivotal support for the fuseholder assembly.

A lower contact having a projecting portion 15 may be affixed to the support 14 in such a manner that it normally engages an extending portion of the contact sleeve 32. Upper and lower terminal connectors may also be provided on the upper contact assembly 13 and in the vicinity of the lower contact 15 but only the upper of these is shown as they are well known in the art.

When the fuseholder 16 is in circuit bridging position the trunnions 34 are received in bearing members 41, the fuseholder projecting off-set contacts 25 are received between the legs of contact 20, the latch 27 positively engages latching lug 22 and the flip out lever 36 engages link 17 with legs 37 straddling the arm 30 of sleeve 28. When legs 37 straddle arm 31) the lugs 29 abut against one end (the left end relative to FIG. 1) of the slot 33 shown in FIG. 1 and against the right end of the opposed slot 33. It can thusly be seen that no torsional movement of the fuse tube 16 and inner sleeve 28 relative to outer sleeve 32 is possible as long as legs 37 of lever 36 straddle the arm 30. Since the fuse tube cannot rotate about its axis the effect of the leaf spring 21 on the off-set contact portions 25 is overcome in this position.

In the event of a fault current the link 17 ruptures within the tube 16' and deionizing gases are evolved from the fuse tube to extinguish the electrical are drawn between ruptured ends of the link. Meanwhile the spring biased flip out lever 36 rotates in a clockwise direction relative to FIG. 1 under the force of spring 36 thereby withdrawing one end of the ruptured link from the fuse tube. As the lever 36 rotates in a clockwise direction relative to FIG. 1 the legs 37 move from the straddling position on either side of arm 30. Thence, the pressure of the upper contact and spring, and 21 respectively, on the fuseholder offset contacts 25, serves to rotate the fuse tube around its vertical axis (torsional rotation) until lugs 29 impinge on the other side of the slot 33 (right side of slot shown in FIG. 1 and left side of the other slot).

Note especially that no torsional rotation of the fuse tube and upper contact can occur until the lever 36 moves around its pivot (35) since up to this time the arm 30 is prevented from moving by the legs 37 of the lever 36. In this respect the roller 31 aids in allowing the lever 36 to move when the lever is released by rupturing of fuse link 17, since the roller 31 moves over a vertical portion of one of the legs 37 thusly preventing any tendency of binding, etc. therebetween.

After the lever 36 has rotated (clockwise relative to PEG. 1) about its pivot (35) and as the fuse tube 16', inner sleeve 28 and upper contacts 25 rotate about the vertical axis of the tube under the force exerted by the member 21 the latch 27 moves out of engagement with lug 22 and the pressure exerted by the contact and spring 21 on the fuse tube upper contacts reaches zero thereby allowing the fuse tube to pivot (drop out) on the trnnnions out of circuit bridging relation.

I have found that this construction virtually eliminates contact burning and pitting since the only relative movement of the upper fixed and movable contacts prior to are extinction is a wiping action over a relatively large contact area, while no relative motion occurs between the lower fixed and movable contacts until the fuseholder starts to drop open out of circuit bridging relation. It is to be noted that if the fuseholder 16- is resiliently mounted on the insulator 12 that the wiping action above referred to may be occasioned by axial as well as rotative movement of the fuse tube and upper contact. In this case portion 19' of hood 19 acts as a stop by con tacting the upper portion of contact portion 25 to prevent excessive axial travel of the fuse tube and upper contact in an upward direction.

Since the upper spring of this invention need not be a quick travel spring there is little or no chance of spring malfunction or spring slowness causing premature contact separation. This construction also provides a slight time delay after the flip out lever has pivoted thereby withdrawing one end of the link from the tube, and before the fuseholder pivots on the trunnions out of circuit bridging position, in which throughout the delay, upper contact engagement is maintained.

While one particular embodiment of the invention has been shown and described, it will be obvious to those skilled in the art that various changes and modifications can be made therefrom without departing from the invention and, therefore, it is intended for the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

1. A fuse cutout comprising, in combination, a lower stationary contact, upper spaced apart inwardly biased stationary contacts, a lower fuseholder support, a fuseholder including a gas evolving fuse tube having a rupturable fuse link therewithin electrically bridging said upper and lower contacts, said fuseholder having offset pro jecting contacts integral therewith which are normally engaged between said upper spaced apart stationary contacts, latching means engaging said fuseholder for nor mally maintaining said fuseholder in circuit bridging position, a first sleeve member rigidly affixed to said fuse tube, said first sleeve member having at least one projecting lug and a transversely extending arm portion, a second sleeve member surrounding said first sleeve, said second sleeve having means thereon for receiving said projecting lug so that said second sleeve is supported by said lug on said first sleeve and said first sleeve and said fuse tube are rotationally movable with respect to said second sleeve, said second sleeve having trunnion means thereon for pivotally engaging said lower fuseholder support, and spring biased fuse link flip out means pivotally mounted on said second sleeve and normally engaging a portion of said fuse link so as to exert a tensile force on said link, said flip out means having leg portions which normally straddle said transversely extending arm portion on said first sleeve to prevent rotation thereof with respect to said second sleeve, whereby upon rupture of said fuse link said flip out means pivots with respect to said second sleeve allowing said fuse tube to subsequently rotate about its axis under the force exerted by said inwardly biased stationary contacts on said off-set projecting contacts thereby disengaging said latching means and allowing said fuseholder to pivot out of circuit bridging position.

2. A fuse cutout having, spaced apart upper and lower stationary contacts, said upper contacts being oppositely disposed and inwardly biased one to another, a lower fuse tube support, a gas evolving fuse tube having a rupturable current responsive element therewithin electrically bridging said spaced apart contacts, upper off-set contact surfaces aflixed to said fuse tube and normally received between said upper stationary contacts, a first member affixed to said fuse tube and having a transversely extending arm portion and a projecting portion, a second member surrounding said first affixed member and having means associated therewith which cooperate with said projecting portion on said first member to prevent axial movement of said fuse tube relative to said second member and to allow limited torsional rotation of said fuse tube relative to said second member, said second member having mean thereon for pivotally engaging said lower fuse tube support, and spring biased extractor means pivotally mounted on said second member normally engaging a portion of said current responsive element and engaging said transverse arm portion of said first member to prevent rotation thereof, whereby subsequent to rupture of said current responsive element said flip out means pivots out of engagement with said transverse arm portion to allow said upper inwardly biased contacts to effect torsional rotation of said fuse tube and thereby permit said fuse tube to move out of contact bridging position.

3. A fuse cutout comprising an insulating member, upper stationary contacts oppositely disposed to one another and inwardly biased one to another, lower stationary contacts spaced apart from said upper contacts, a fuseholder assembly including a gas evolving fuse tube having a rupturable fuse link electrically bridging said upper and lower contacts, means for supporting said fuseholder assembly relative to said insulating member, upper off-set contact surfaces affixed to said fuse tube and normally received between said upper stationary contacts, latching means engaging said fuse tube for normally maintaining said fuse tube in circuit bridging position, conductive sleeve means surrounding said fuse tube and pivotally engaging said support means for preventing axial movement of said fuse tube while permitting torsional movement thereof, and link extracting means mounted on said sleeve means and having a first position for preventing torsional movement of said fuse tube and a second position for extracting a portion of said fuse link from said fuse tube and for allowing torsional movement of said fuse tube, whereby upon fuse link rupture said extracting means pivots relative to said sleeve means withdrawing said link from said fuse tube thereby allowing said fuse tube to axially rotate out of engagement with said latching means and to subsequently pivot out of contact bridging position.

4. A fuse cutout comprising, in combination, an insulating member, upper and lower stationary contacts, said upper contacts being oppositely disposed and inwardly biased one to another, a fuseholder assembly including a fuse tube and a conducting member therewithin electrically bridging said upper and lower contacts, a portion of said conducting member being a rupturable current responsive element, means for supporting said fuseholder assembly relative to said insulating member, upper off-set contact surfaces aflixed to said fuse tube and normally received between said upper contacts, means engaging said fuse tube and pivot-ally engaging said support means for preventing axial movement of said fuse tube with respect to said support means while permitting limited axial rotation thereof, and lever means engaging said conducting member and pivotally mounted on said means engaging said fuse tube for preventing axial rotation of said fuse tube prior to rupture of said current responsive element, whereby upon current responsive element rupture said lever means pivots about said engaging means allowing said inwardly biased contacts to effect axial rotation of said fuse tube thereby permitting said fuseholder assembly to move out of stationary contact bridging position.

5. A fuse cutout comprising, in combination, an insulating member, spaced apart stationary contact means, a fuseholder including a fuse tube having a rupturable current responsive element therein electrically bridging the space between said stationary contacts, means for supporting said fuseholder relative to said insulating member, said fuseholder being pivotable about said means for movement into and out of contact bridging position, contact means rigidly atfixed to said fuse tube and normally engaging one of said stationary contact means, latch means for normally maintaining said fuseholder in contact bridging position, motion imparting means associated with one of said stationary contact means for imparting a torsional force to said fuse tube, electrically conductive means embracing said fuse tube and pivotally engaging said fuseholder support for preventing axial movement of said fuse tube with respect to said insulating member while permitting torsional movement thereof, extractor means pivotally mounted on said embracing means, said extractor means having a first position for exerting a tensile force on said current responsive element and for preventing rotation of said fuse tube and a second position for removing a portion of said current responsive element from said fuse tube and for permitting rotation of said fuse tube, whereby upon rupture of said current responsive element said extractor means moves from said first to said second position thereby permitting said fuse tube to rotate under the impetus of the force exerted by said motion imparting means and to subsequently become unlatched and allow s-aid fuseholder to pivot out of contact bridging position.

6. A current interrupting device comprising insulating means, spaced apart relatively stationary contact means, a fuse assembly including a fuse tube having spaced apart contact means normally in electrical engagement with said stationary contact means and a rupturable conducting member electrically bridging said contact means, means for normally imparting a tersional thrust to said fuse tube, latching means for normally maintaining the engagement between said contact means and said stationary contact means, and means associated with said fuse tube for normally exerting a tension on said rupturable conducting member, said means having a first position for preventing torsional rotation of said tube and a second position for allowing torsional rotation of said tube and being movable between said first and second positions subsequent to rupture of said rupturable conducting member to allow said latching means to become disengaged and to allow said contact means to be disengaged from said stationary contact means.

7. A current interrupting device comprising insulating means having associated therewith spaced apart relatively stationary contact means, a fuseholder assembly including -a current responsive rupturable conducting member for normally electrically bridging said stationary contact means, means associated 'with at least one of said stationary contact means for normally urging at least a portion of said fuseholder assembly toward axial rotation, latching means for normally maintaining said fuseholder assembly in circuit bridging position, means constructed and arranged in such a manner that in one position it prevents axial rotation of said fuseholder assembly, while in another position it permits axial rotation of said fuseholder assembly under the impetus of said urging means,

7 '8 said means being retained in said one position by said 9. The device of claim 7 wherein said means urging rupturable conducting member and being movable to said said fuseholder assembly toward axial rotation is a reother position subsequent to rupture of said conducting silient member positioned in close proximity to one of member, whereby upon axial rotation of said fusebolder said spaced'apart relatively stationary contact means.

assembly said latching means is disengaged and said fuse- 5 holder assembly is allowed to move from circuit bridging References cued m the file of thls patent position UNITED STATES PATENTS 8. The device of claim 7 wherein said means urging 2,134,075 Dey Oct. 25, 1938 said fuseholder assembly toward axial rotation constitutes 2,484,839 Lindell Oct. 18, 1949 one of said spaced apart relatively stationary contact 10 2,578,255 Lindell Dec. 11, 1951 means. 2,910,560 Stroup et a1 Oct. 27, 1959

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