US3177317A - Drop out fuse construction having a fuse tube which is resiliently mounted in an annular support member - Google Patents

Description

Aprll 6, 1965 R. M CLOUD 3,177,317

DROP OUT FUSE CONSTRUCTION HAVING A FUSE TUBE WHICH IS RESILIENTLY MOUNTED IN AN ANNULAR SUPPORT MEMBER Filed July 22,1960 2 Sheets-Sheet I IN V EN TOR. kaea: A. flfckaua Y April 6, 1965 MCCLQUD 3,177,317

DROP OUT FUSE CONSTRUCTION HAVING A FUSE TUBE WHICH IS RESILIENTLY MOUNTED IN AN ANNULAR SUPPORT MEMBER Filed July 22, 1960 2 Sheets-Sheet 2 IN V EN TOR.

yamwfw United States Patent 3,177,317 Dlifil @UT FUSE CflNfiTRUQTlUN HAVHNG A FUSE TUBE WHMIH l) RESELEENTLY MGUNTED IN AN ANNULAR SUEPGRT MEMBER George R. McCloud, hearth lt lilwauhee, Win, assignor to MeGraw-Edison Company, Milwaukee, Wis, a corporation of Delaware Filed fully 2.2, 196d, Ser. No. dhtitiil 8 Qlaims. (Cl. Nth-114) This invention relates generally to fuse cutouts and more particularly to an improved fuse cutout wherein recoil forces developed incident to current interruption are dissipated in the fuse tube itself.

Generally fuse cutouts are so constructed that upon over-currents the fuse link within the fuse tube ruptures causing an arc to be drawn between the severed ends of the link. The arc so created induces a significant temperature rise within the fuse tube which causes the fuse tube or fuse liner to evolve deionizing gases from the inner surface thereof. The gases so evolved tend to extinguish the arc and to thereby interrupt the flow of current through the fuse tube.

The gases, in evolving at an extremely rapid rate within the limited confines of the fuse tube bore, develop a relatively high pressure. Hence provisions are made to vent the fuse tube thusly allowing the generated gases to escape therefrom. Commonly one end of the fuse tube is left open and an expendable cap (similar to that described in Patent No. 2,702,842 issued February 22, 1955 to lepsen et al., and assigned to the same assignee as the present invention) is utilized to close the other end of the tube. This construction provides single vented operations on low fault currents and double vented operation on relatively higher fault current conditions. During high current interruption in a fuse cutout utilizing an expendable cap on the upper end of the fuse tube, the gases initially escaping from the lower end of the tube impart an upward thrust to the tube. After the expendable cap has blown the thrust is generallyreversed i.e., a downward force is exerted on the fuse tube.

In the case of single vented fuse tubes (those not utilizing an expendable cap) the thrust is generally unidirectional. (O-pposite to the direction of the escaping gases.)

In either event, sometime during the current interrupting cycle, a relatively large thrust force is exerted on the fuse tube and the cutout assembly in general.

Prior art fuse cutouts have attempted to realize structures which will absorb or otherwise dissipate this thrust force. 7

One means of dissipating thrust forces, quite frequently used by the prior art devices, is to make the component parts of the cutout larger and more capable of absorbing impact forces. However, this is expensive and results in bulky oversized cutouts.

Another method of dissipating thrust forces is to mount the fuse tube on the porcelain insulator by means of a resilient support member. While deformation of the support member serves to absorb some of the recoil forces, in practice, a portion of these forces must normally be absorbed by the porcelain insulator, a condition which may lead to rupture of the porcelain.

I have found that by resiliently mounting the fuse tube with respect to its supporting members and the rest of the cutout that a maximum amount of thrust dissipation may be achieved at a minimal cost.

It is therefore an object of this invention to provide a fuse cutout wherein thrust forces are substantially dis sipated in moving the fuse tube relative to the rest of the cutout.

Another object of the invention is to provide a fuse cutout that is inexpensive to build and which has very little tendency to malfunction.

A further object of the invention is to provide a fuse cutout that functions to effectively dissipate thrust forces occurring in both directions along the fuse tube.

A still further object of the invention is to provide a fuse cutout wherein premature separation of contacts is substantially eliminated.

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 cutaway view in elevation of the invention;

FIG. 2 is a partially cut away view in elevation of a portion of the device of FIG. 1.

FIG. 3 is a partially cutaway view in elevation of one embodiment of the invention.

Referring now to FIG. 1 there is shown a fuse cutout indicated generally as 1 and comprising a porcelain insulator 2 having aflixed thereto an upper contact assembly 3 and lower trunnion supports 4 and a fuse tube assembly 5 bridging the space between members 3 and 4.

The upper contact assembly 3 comprises a support member 6 which is ailixed to insulator 2 by means of through bolt 7 and nut is. An L-shaped member d is attached to support 6 by fastening means it and extends upwardly of the insulator 2. A terminal reception member may be attached to the upward extremity of member to receive a line wire but this is not shown.

Aflixed to support a is a hood member 11 which has a curvate top portion 12 with a slot 1.3 therein and a pair of laterally projecting side portions 14. Attached to the underside of the inwardly projecting leg 15 of L-shaped member 9 is a pair of curvate spring contacts 16 which generally follow the configuration of the curvate top portion 12 of the hood 11. Enlarged contact faces 17 may be provided at the free end of contacts 16 in order to increase the contact area.

A spring biased latch 18 is pivotally affixed to support member 6 and extends between contacts 16 and through slot 13 in top 12 and is adapted to move along the axis of the slot. The latch 18 is provided wtih a cut away face portion 18' and a locking shoulder portion 19 behind the face of the latch.

A member 20 is afiixed to the upper end of a fuse tube 21 and has a ferrule portion 22 containing a bore 23 therein which communicates with the interior of the fuse tube 21. The other end of the bore 23 may be enclosed by an expendable cap 24-. Extending transversely from member 2i is a contact arm 25 having an enlarged contact facial surface 26 on the end thereof. Immediately behind the facial surface 26 is a shoulder portion 27 which is adapted to normally engage the shoulder portion 19 of latch 18 to provide positive locking therebetween. It can be seen that when latch 18 and contact 25 are in engagement with one another that contact facial surface 26 is in contact with the enlarged contact faces 17 of spring contacts 16.

Pivotally attached to member 2% by means of a pivot pin 20 is an integral pull ring and unlatching member 28 which comprises a pull ring 29 on one side of pin 2b and an elongate unlatching arm 39 which is normally in com tact with th elower surface of latch 18. Thusly when the fuse tube 21 is in circuit bridging position, downward movement on pull ring 29 will cause arm 34) to force latch 13 upwardly allowing the fuse tube assembly to become unlatched.

Surrounding the lower end of fuse tube 21 is a sleeve member 31. The sleeve member 31 has a laterally projecting portion 32 (FIG. 2) which is shouldered at its outer end at 33. A portion of the member 31 is removed at 34 so that entrance may be made to a portion of the fuse tube 21 within the sleeve. A collar member 35 is firmly aflixcd to the lower area of the fuse tube 21 as by fastening means 36.

The bore through the sleeve member 31 is increased in steps to the middle of the member and thence decreased in the same manner. The annular shoulders so created are delineated as 37, 38, 38' and 37.

Helical compression springs 39 and 4t) are attached to the top and bottom of collar 35 and surround a portion of the fuse tube 21. The upper spring 39 is bottomed at its upper end against shoulder 37 of member 31 and the lower spring 40 is bottomed at its lower end against shoulder 37' of member 31.

Thusly fuse tube 21 is floating within the sleeve 31 and is capable of axial movement with respect to the sleeve to the extent that collar 35 can move before abutting against shoulders 38 and 38'.

A pair of diamond shaped lug members 41 project outwardly from both sides of the upper area of sleeve 31. Adjacent the lugs 41 is a through pivot pin 42 which serves as the pivot for hinge contact 43. Hinge 43 has a lip portion 43 near the upper side thereof which is designed to contact lugs 41 and therefore limit the extent of movement between the hinge and sleeve members.

At the lower end of hinge member 43 are a pair of projecting bearing members or trunnions 45 which engage with lower trunnion supports 4 to support the fuse tube assembly.

Spaced inwardly of the bearing members 45 are cammed contact surfaces 46 which normally engage with resilient contacts 47 on the inner side of the lower trunnion supports 4. A pivot pin 48 extends between the bearing members 45 (FIG. 2) and a fuse link fiip out lever 49 is mounted thereon. A torsion spring 50 is also mounted on the pin 48 and normally biases lever 49 in a clockwise direction relative to FIGURE 2.

A lip portion 51 is provided on lever 49 and is adapted to engage with shoulder 33 on sleeve 31 to prevent relative motion between the sleeve 31 and hinge 43. That is, when a fuse link 52 is positioned within the tube 21 and anchored at its lower end to the hinge member thereby drawing up lever 49 against the action of spring 50, the engagement of lip 51 and shoulder 33 will prevent movement between the sleeve and hinge until the fuse link is ruptured thereby allowing the lever to pivot out of locking engagement with the sleeve.

When the fuse link is ruptured the flip out lever 49 pivots out of engagement with the sleeve, the hinge 43 pivots around pin 42 and trunnions 45 and the fuse tube drops down until the diamond shaped lug 41 and lip 43' interengage at which time the hinge and fuse tube pivot around trunnions 45 as a unit in a clockwise direction.

It should be noted that the nature of the contact between the upper resilient contacts and the upper contact on the fuse tube is a wiping action so that axial movement of the tube will not break contact engagement.

In operation when a fault current is experienced the fuse link ruptures, an arc is struck, gases are evolved from the fuse tube tending to extinguish the are and then gases are vented from the tube with an accompanying thrust force on the tube.

This thrust force is largely absorbed by compression of the springs 39 and 40 since energy is required to move the tube against the biasing action of the springs.

Typically the predominant thrust will be directed in an upward direction thusly compressing spring 39. When the spring reaches maximum compression or when collar 35 abuts against annular shoulder 38 the fuse tube and collar will tend to be forced in the opposite direction which will cause compression of the spring 40. It the case of a cutout utilizing an expendable cap the sequence of spring action is first compression of spring 39 then after the cap blows compression of spring 40. Each time one or the A other of the springs is compressed work is done and forces dissipated in so doing. Note that each time one of the springs is compressed the other of the springs is elongated (tensioned) thusly adding to the energy dissipated.

It is important that the springs 39 and 4t be so coordinated that the collar member is normally positioned midway between the annular shoulders 33, 38. In this respect the lower spring 4% may be somewhat higher rated than the upper spring since the force of spring latch 18 and the weight of fuse tube 21 normally tend to compress the lower spring.

While two compression springs are shown it is possible, particularly on single vented cutouts, to eliminate one of the springs since movement of the tube under the impetus of the force exerted by the escaping gases is in general uni-directional.

I have found that by using the heretofore described structure that very little recoil is experienced in the component parts of the fuse cutout other than in the fuse tube, the movement of which is designed to dissipate thrust forces.

In addition cutouts constructed according to this principle suffer little or no hangar bracket detformation, porcelain rupture, or other comparable structural failures.

The embodiment of FIGURE 3 is similar to that of FIGS. 1 and 2 except that the springs 39 and 4d are replaced by a shock isolator 61 which may be of rubber, plastic or any other shock absorbing material.

Member 31 of FIG. 3 has an enlarged bore 66 therein. Afiixed to the. sides of the bore 60 is a thick inner layer in of rubber, plastic or a similar material which is somewhat resilient and shock absorbent and which has the capacity of acting as a shock isolator. The fuse tube 21 extends through the shock isolator 61 and has affixed thereto at positions above and below the layer 61 nuts or collar means 62 or similar members which overlie a portion of the layer 61. A portion 32 of the member 31 projects laterally from the fuse tube and culminates in a shoulder 33' which as before is adapted to engage a portion of the flip out lever 49. A hinge like that of FIGS. 1 and 2 (43) is pivotally attached to the sleeve 31 in the same manner as before but this is not shown.

The modification of FIG. 3 operates in the same manner as that of FIGS. 1 and 2 except that thrust energy is expended in compressing first one end and then the other of the layer 61. This particular modification has the advantage that in not having springs the damage due to corrosion will be reduced.

While the layer 61 is indicated as being afiixed to the member 31 and in frictional engagement with tube 21, it is within the scope of this invention to affix the layer to both the sleeve and fuse tube thereby eliminating the collar members but this is not shown.

Both embodiments serve to substantially dissipate the thrust on the fuse tube without experiencing destruction or fatigue of component parts or premature fuse tube or contact separation.

While two particular embodiments of the invention have 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. In combination with a dropout expulsion fuse cutout having an elongated insulating member, a lower stationary contact and a spring biased upper stationary contact mounted in spaced apart relation on said insulating member, a gas evolving expulsion fuse tube, an upper movable contact on said fuse tube normally engaging said spring biased contact and being continuously engageable therewith through limited axial displacement of said fuse tube, and a rupturable fuse link extending axially through said fuse tube and being electrically connected to said upper movable contact and normally electrically bridging said lower and upper stationary contacts; a sleeve member supported on said lower stationary contact and being in radially spaced apart surrounding relation to the lower end of said fuse tube, an annular member of shock absorbing material having its external surface affixed to the bore of said sleeve member and its internal surface in con tiguous surrounding relation to said fuse tube, means on said fuse tube for engaging said member of shock absorbing material so that said fuse tube is supported in a normal position relative to said sleeve member against axial displacement in upward and downward directions, said fuse tube being free to move axially relative to said sleeve member and said member of shock absorbing material returning said fuse tube to said normal position after the thrust forces resulting from expulsion of gas from said fuse tube incident to rupture of said fuse link subside, whereby said thrust forces are substantially dissipated by axial upward and downward displacement of said fuse tube against said member of shock absorbing material.

2. In a fuse cutout, an elongated insulating member, a lower stationary contact and a spring biased upper stationary contact mounted in spaced apart relation on said insulating member, a gas evolving expulsion fuse tube, an upper con-tact affixed to said fuse tube and normally engaging said spring biased contact, said upper and said spring biased contacts being in continuous engagement through limited axial displacement of said fuse tube, a hinge contact member supported on said lower stationary contact, a sleeve member surrounding the lower end of said fuse tube and being pivotally mounted on said hinge contact member and having upper and lower radially extending surfaces adjacent its upper lower ends, said fuse tube being free to move axially relative to said sleeve member, a rupturable fuse link extending axially through said fuse tube and being electrically connected to said upper contact and to said hinge contact member and normally electrically bridging said upper and lower stationary contacts, a collar member rigidly affixed to said fuse tube and disposed intermediate said upper and lower radially extending surfaces on said sleeve member, first and second spring means surrounding said fuse tube and being disposed between said collar and said upper and lower radially extending surfaces respectively and supporting said fuse tube in a normal position relative to said sleeve member against axial displacement in upward and downward directions under the thrust forces resulting from expulsion of gas from said fuse tube incident to rupture of said fuse link and returning said fuse tube to said normal position after said thrust forces subside.

3. In an open fuse cutout, an elongated insulating member, a lower stationary contact and a spring biased upper stationary contact mounted in spaced apart relation on said insulating member, a gas evolving expulsion fuse tube, upper contact means afixed to said fuse tube and normally engaging said spring biased contact, said upper contact means and said spring biased contact being in continuous engagement through limited axial displacement of said fuse tube, a rupturable fuse link extending axially through said fuse tube and being electrically connected to said upper contact means and electrically bridging said lower and upper stationary contacts, a support member supported on said lower stationary contact and surrounding at least a portion of said fuse tube, said fuse tube being free to move axially relative to said support member, and resilient means interconnecting said fuse tube and said support member and supporting said fuse tube in a normal position relative to said support member against axial displacement in upward and downward directions and being adapted to be deformed upon axial displacement of said fuse tube resulting from expulsion of gas from said fuse tube incident to rupture of said fuse link and returning said fuse tube to said normal position after expulsion of gas from said fuse tube has ceased, whereby recoil forces resulting from expulsion of gas from said fuse tube are dissipated in said resilient means.

4. In a dropout fuse cutout, an elongated insulating member, a gas evolving expulsion fuse tube, an upper contact affixed to said fuse tube, a lower stationary contact on said insulating member, a spring biased upper stationary contact mounted on said insulating member in spaced apart relation to said lower stationary contact and being adapted to remain in continuous engagement with said upper contact on said fuse tube during limited axial displacement of said fuse tube, a hinge contact member supported on said lower stationary contact, a rupturable fuse link within said fuse tube connected to said upper contact and bridging said upper and lower stationary contacts, an arcuate member disposed in surrounding relation to a portion of said fuse tube and pivotally connected to said hinge contact member, collar means rigidly affixed to said fuse tube, resilient means surrounding said fuse tube and engaging said arcuate member and said collar means for supporting said fuse tube in a normal position relative to said arcuate member and resiliently opposing upward and downward displacement of said fuse tube relative to said arcuate member under thrust forces resulting from expulsion of gas from said fuse tube and returning said fuse tube to said normal position relative to said arcuate member after said thrust forces have subsided, whereby said thrust forces are dissipated by bi-directional axial movement of said fuse tube against said resilient means.

5. In an expulsion fuse cutout having an elongated insulator, upper and lower stationary contacts mounted in spaced apart relation on said insulator, and a rupturable fuse link electrically bridging said upper and lower stationary contacts, and a gas evolving expulsion fuse tube surrounding said fuse link; a thrust absorbing device including a member pivotally supported on said lower stationary contact and at least partially surrounding said fuse tube and being movable relative to said fuse tube in a direction parallel to the axis of said fuse tube, and means for resiliently interconnecting said fuse tube and said member and for supporting said fuse tube in a normal position relative to said member against axial displacement under the recoil force caused by expulsion of gas from said fuse tube and returning said fuse tube to said normal position after said recoil force has subsided, whereby displacement of said fuse tube underthe recoil force incident to rupture of said fuse link deforms said supportin means and absorbs said recoil force.

6. In combination with an open type fuse cutout wherein an expulsion fuse tube surrounding a rupturable fuse element is hingedly supported adjacent its lower end on the lower stationary contact of the cutout; a sleeve member surrounding said fuse tube adjacent the lower end, means for supporting said sleeve member on said lower stationary contact, recoil absorbing means disposed between said fuse tube and said sleeve member for resiliently supporting said fuse tube in a normal position relative to said sleeve member so that said fuse tube is free to move relative to said sleeve member and is axially displaceable in upward and downward directions relative to said sleeve member, means on said fuse tube for engaging a first po tion of said recoil absorbing means, and means on said sleeve member for engaging a second portion of said recoil absorbing means spaced from said first portion, said recoil absorbing means being stressed in response to displacement of said fuse tube incident to rupture of said fuse element and expulsion of gas from said fuse tube and being stressed to a relatively less degree when said fuse tube is in said normal position and returning said fuse tube to said normal position after said fuse element ruptures and the arc is interrupted, whereby recoil forces exerted on said fuse tube are dissipated in said recoil absorbing means and are not transmitted to said lower stationary contact.

7. In the combination defined by claim 6 wherein said recoil absorbing means includes an annular member of elastic shock absorbing material aflixed to the inner periphery of said sleeve member.

8. In the combination defined by claim 6 wherein one of said means for engaging said recoil absorbing means includes collar means and said recoil absorbing means includes first and second compression springs surrounding said fuse tube and abutting against opposite sides of said collar means.

Relierences Cited by the Examiner UNITED STATES PATENTS 2,328,745 9/43 Sandin 200-114 5 2,519,289 8/50 Roman et a1 200-114 2,544,491 3 /51 Davis 200-166 2,689,284 9/54 Hill 200-114 2,877,320 3/59 Hill 200-114 BERNARD A. GILHEANY, Primary Examinen 10 RICHARD M. WOOD, Examiner.

Claims (1)

1. 5. IN AN EXPULSION FUSE CUTOUT HAVING AN ELONGATED INSULATOR, UPPER AND LOWER STATIONARY CONTACTS MOUNTED IN SPACED APART RELATION ON SAID INSULATOR, AND A RUPTURABLE FUSE LINK ELECTRICALLY BRIDGING SAID UPPER AND LOWER STATIONARY CONTACTS, AND A GAS EVOLVING EXPULSION FUSE TUBE SURROUNDING SAID FUSE LINK; A THRUST ABSORBING DEVICE INCLUDING A MEMBER PIVOTALLY SUPPORTED ON SAID LOWER STATIONARY CONTACT AND AT LEAST PARTIALLY SURROUNDING SAID FUSE TUBE AND BEING MOVABLE RELATIVE TO SAID FUSE TUBE IN A DIRECTION PARALLEL TO THE AXIS OF SAID FUSE TUBE, AND MEANS FOR RESILIENTLY INTERCONNECTING SAID FUSE TUBE AND SAID MEMBER AND FOR SUPPORTING SAID FUSE TUBE IN A NORMAL POSITION RELATIVE TO SAID MEMBER AGAINST AXIAL DISPLACEMENT UNDER THE RECOIL FORCE CAUSED BY EXPULSION OF GAS FROM SAID FUSE TUBE AND RETURNING SAID FUSE TUBE TO SAID NORMAL POSITION AFTER SAID RECOIL FORCE HAS SUBSIDED, WHEREBY DISPLACEMENT OF SAID FUSE TUBE UNDER THE RECOIL FORCE INCIDENT TO RUPTURE OF SAID FUSE LINK DEFORMS SAID SUPPORTING MEANS AND ABSORBS SAID RECOIL FORCE.

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