US3002070A

US3002070A - Fuse cutout

Info

Publication number: US3002070A
Application number: US53473A
Authority: US
Inventors: Raymond J Bronikowski; George R Mccloud
Original assignee: McGraw Edison Co
Current assignee: McGraw Edison Co
Priority date: 1960-09-01
Filing date: 1960-09-01
Publication date: 1961-09-26
Anticipated expiration: 1978-09-26

Description

P 1961 R. J. BRONlKOWSKl ETAL 3,002,070

FUSE CUTOUT 3 Sheets-Sheet 1 Filed Sept. 1, 1960,

IM WU INVENTORS, RfifMQ/VD a; aio/w/(oa/sx/ 650,666 A Macaw/p Sept. 26, 1961 R. J. BROVNIKOWSKI ETAL 7 FUSE CUTOUT 3 Sheets-Sheet 2 Filed Sept. 1, 1960 INVENTORS. R14) MU/VD J: EPaN/KOWSK/ GEO/Q65 f? MCCLOC/fl Sept. 26, 1961 R, J. BRONIKOWSKI ETAL 3,002,070

FUSE CUTOUT Filed Sept. 1, 1960 5 Sheets-Sheet 5 United States Patent 3,002,070 FUSE CUTOUT I Raymond J. Bronikowski and George R. McCloud, South Milwaukee, Wis., assignors to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Filed Sept. 1, 1960, Ser. No. 53,473 4 Claims. (Cl. 200-114) This invention relatesto improvements in fuse cutout assemblies and more specifically to improvements in expulsion type fuse cutout assemblies. 7

The use of electrical power has been and is increasing at a phenomenal rate. As the use of electrical power increases the capacities of power distribution system also are increased in order to meet the demand for electrical power. Accompanying the increased power system capacities are higher values of system fault current. In order to insure the proper protection of present day and future power systems, fuse cutouts having higher interrupting requirements are a necessity. These fuse .cut

3,002,070 Patented Sept. 26, 1961 tube is a function of the internal bore of the fuse tube that an increase in fuse tube internal bore would be acouts must be capable of operating under a full range of faults from slight overloads through the highest interrupting ratings. Further, in order to meet the acceptedin dustry standards, expulsion cutouts must clear the maximum rating of the cutout a minimum of five successive times and be capable, after the fifth such interruption, of carrying the rated value of continuous current.

In interrupting fault currents in a fibre lined expulsion fuse a great deal of gas (generally carbon monoxide, water vapor, methane and hydrogen) is evolved from the fibre surface of the fuse tube as a result of the heat generated by the electrical arc. The evolved gases are in a turbulent state and develop high pressures and serve to extinguish the electrical arc developed between portions of the fuse link after the fusible section of the fuse link melts as result of the fault current. The so evolved gases will vent from the open end of the fuse tube (generally the bottom) and if an expendable cap is utilized, subsequently at a higher pressure, also vent from the other end of the fuse tube (generally the top).

the pressure therein may be in the thousands of p.s.i. and as gas and other particles are vented from the fuse tube a thrust which may be in excess of 2000 pounds maybe developed. The thrust on the fuse tube, which is a time function dependent on current and arcing period, is like that of any jet device in that it is opposite in direction to the gases being expelled from the fusetube. I

Single vented cutouts (vented at the bottom) experience a great deal of recoil at high currents since the thrust developed is substantially unidirectional (orupward) and the fuse cut-out itself 'must resist the thrust forces. Double vented cutouts (utilizing a cap similar to that of the Jepsen et al. patent, No. 2,702,842, issued February 22, 1955) experience the same unbalanced thrust as single vented cutouts until the expendable cap ruptures. When the expendable cap ruptures venting takes place at both ends of the tube and, the thrust developed at one end of the fuse tube tends to nullify the thrust developed at the other end of the tube. In this manner unbalanced thrust is minimized and as a result interrupting rating increases of 100% or more have been achieved in double vented cutouts as compared to single vented cutouts.

Since unbalanced thrust forces are negligible during double venting, the problem of compensating for thrust forces is of primary concern during single vented operation.

Another method of decreasing fuse tubethrust (other than thru the use of an expendable cap) has been to increase the bore of the fuse tube. One might expect that Since the pressure of the evolved gases within the fuse 40 During the evolvement of gases within the fuse tube companied by a decrease in gas pressure. Further, one might expect that since fuse tube thrust is a function of gas pressure within the fuse tube according to the formula T= V%+PA where represents the mass flow rate of gas and metal particles,

A the fuse tube cross-sectional area, and P the pressure at the end of the tube, that a decrease in internal gas pressure will be accompanied by a comparable thrust reduction. Despite this, however, thrust reduction realized according to this theory, by prior art devices, has not been dramatic owing to the fact that as the internal volume of the fuse tube per unit length increases according to the formula the area of gas evolving fibre per unit length exposed to p the arc increases linearly with diameter according to the formula A=1rD. Thusly even though a larger internal tube volume is achieved a larger amount of tube wall has achieved this modest reduction at the expense of the low current clearing ability of the cutout. Therefore, by and large this whole approach to the problem of thrust reduction is inadequate. p

Other attempts to reduce the thrust effects on the cutout have utilized cutout structures designed so as to reduce the recoil effect on the pole support member and cutout support hangerbracket, during and just after arcing, by providing for relative motion between the fuse tube and other portions of the cutout. To achieve this the fuse tube is often resiliently mounted with respect to the insulator and hence the fuse tube moves a relatively great distance under the impetus of thrust before it c01- lides with other portions of the cutout.

Kinetic energy developed as a result of the motion of the fuse tube or other various portions of the cutout relative to one another must be absorbed byeither (1) The mounting bracket. 7

, (2) The cross-arm support hardware, or

(3) Some other relatively elastic member in the supporting structure.

This absorption or dissipation of energy will evidence itself as deflection of one or more of the foregoing parts. It is when these parts are subjected to stresses beyond their elastic limit that permanent deformation and fracture of parts occur which may result in cutout failure.

- A large portion of this developed kinetic energy in prior art devices is dissipated upon collision of different portions of the cutout. Since such prior art constructions rely on these collisions to dissipate a portion of the kinetic energy developed, these constructions quite often become damaged when utilized to interrupt relatively high fault currents (single vented operation) since the high value of thrust developed in the tube imparts a high velocity to themovingparts which leads to highly dama collisions. These collisions in rior art de-g gmg P vices frequently cause porcelain rupture, electrical contact damage, and the like, all of which render the cutout unfit for further duty without extensive parts replacement or thereplacement of the entire cutout.

As the range of single vented cutout interrupting ratings increases the severity and nature of these damaging collisions also increase, bearing witness to the fact that the problem of cutout recoil cannot be feasibly solved in this manner. We have also found that prior art devices which permit free motion of the fuse tube actually increase the amount of kinetic energy to be dissipated.

v a portion of the cutout of FIG. 2 taken along the lines While the fuse tube is a relatively small mass, a high velocity can be imparted to it as a result of the thrust force developed in the tube. Since kinetic energy is equal to /2MV any increase in the velocity of the fuse tube under the impetus ofthe thrust forces increases the kinetic energy by the square of the velocity.

In addition to the fact that prior art devices develop high levels of kinetic energy that must be dissipated in one manner or another, the freedom of movement aspects of the fuse tube caused additional difficulties. In permitting relative movement between the fuse cartridge and the remainder of the cutout, quite frequently the movement of the fuse cartridge serves to cause it to become prematurely unlatched from the fuse support and consequently arcing between the. stationary contact and movable contact ensues. This arcing results in substantial burning and pitting of the contacts. Even in these cases where premature unlatching does not occur, considerable relative movement between the contact on the fuse tube and the contact on the fuse support takes place which causes pitting and burning of the contacts and associated structures.

Another serious disadvantage of prior art construc tions is that after the above collisions have occurred much of the kinetic energy of recoil still must be dissipated, and such energy is dissipated in the cross arm or other support member. While a new cross-arm may have suflicient strength to dissipate this energy a crossarm that has been in service for some time may be damaged or wrenched from the upright support under the impetus of these forces.

To obviate the foregoing undesirable features found in prior art fuse cutout this invention has as one of its objects to provide a fuse cutout of low cost andhigh mechanical strength.

7 Another object of the invention is to provide a cutout assembly which develops a minimal amount of kinetic energy as a result of relative movement between portions thereof.

Another object of the invention is to provide a cutout assembly that will serve to effectively interrupt a full range of fault currents and which will interrupt high fault currents without suffering physical and/ or electrical damage.

Another object of the invention is to provide a cutout that will have a maximum interrupting rating and still be capable, after refusing, of interrupting any fault current within its range of ratings.

Another object of the invention is to provide a cutout assembly which permits a maximum of energy absorption in the mounting bracket.

A further object of the invention is to provide a fuse cutout that will remain positively latched during transient conditions.

A further object of the invention is to provide a fuse cutoutthat will suffer little or no burning or pitting of the contacts as a result of fuse tube movement.

A still further object of the invention is to provide a cutout assembly wherein link tension is independent of. contact pressure and/ or fuse tube movement.

Other objects and advantages of our invention Will be apparent from thefollowing description of the preferred. embodiment of the inventiontaken in connection, w th the accompanyingdrawingsin.which;

4-4 of FIG. 2; and

PEG. 5 is an enlarged partially cutaway view in side elevation of a portion of the cutout of FIG. 2 subsequent to link rupture.

Referring now to FIGS. 1 through 3, iii designates a fuse cutout assembly comprising a fuseholder ll, insulator 12 with upper stationary contact and latching means 14, lower support 70 and mounting bracket 13. (The fuseholder consists of a fuse tube and upper and lower contact assemblies 33, 43 respectively.) The fuse tube may be of any of the commonly utilized gas evolving types but thepreferred construction is a thermoset resin-fiber glass reinforced tube having a bone fiber gas evolving have insulating material 16 molded on the bolt head.

The thru bolt 15 and associated nut 17 serve to affix a backing member 18 to the insulator 12.

An L-shaped terminal member 19 is affixed to the.

upper portion of backing member 18 and extends in an axial direction beyond the end of insulator l2 and in a lateral direction away from the insulator. The portion of member 19 extending beyond the end of the insulator preferably has a parallel groove clamp 20 affixed thereto which is adapted to accommodate a conductor (not shown) from either a horizontal or vertical entrance. The L-shaped conducting terminal member 19 and clamp 20 are preferably of non-ferrous construction.

Upper contacts 21 are of generally arcuate configuration and are spaced apart and affixed to the underside of thatportion of L-shaped member 19 which extends laterally from insulator 12. Spring members 2]. are affixed to member 19 and to contacts 21 and are shown as generally following the configuration of the contacts. The purpose of the spring member 21 is to add resiliency to the flexible contacts 21. While contacts and spring members are shown and described it is conceivable that they could be replaced with a single current carrying spring of beryllium copper or Phosphor bronze but this is not shown. An enlarged contact face 21" is provided on the ends of contact 21 most remote from member 19, and serves to bridge the space between contacts 21 as well as serving as a heat sink. The face 21" is preferably silver-plated in order to prevent formation of semiconducting copper oxide on unplated contacts with resultant increased heating during continuous current carrying operation.

A positive latch member 22 is rotatably mounted on the lower end of backing member 18 and extends between the spaced upper contacts 21 and spring members 21. Latch member 22 is normally downwardly biased by a spring 23. A portion 24 of latch member 22 is bifurcated so as'to accommodate latch spring 23 thereinbetween. The bifurcated portion 24 of latch 22 is joined to the rest of the latch by a yoke portion 24. An enlarged face 25 of the latch 22 is chamfered inwardly at an acute angle and a cam-like latching lip 26 is provided in the latch member 22 in the area behind the face 25. An integral stop member 22 projects upwardly from the upper portion of the latch for purposes which will be explained later in the specification. The latch member may be, a non-ferrous casting and is of a relatively small mass. The reasons for the light latch will be further explained later in the description. I

While the latch 22 may be of any material we have found that it is advantageous to, have a conductinglatch and a conducting backing member 18 so that in case the v fuseholder 11 is closed in on a fault, a current path exclusive of the contacts 21, will initially exist. Thusly there is no likelihood in the above circumstance of arcing occurring between conductive portions of the fuseholder and the contacts 21 since the conductinglatch 22will contact the conductive portions of the fuseholder prior to contact by the contacts 21.

A protector hood 27 which maybe of fiber glass re- A thereby tending to hold the release down whereas on opening, the point of application of the force will result in a clockwise moment about the pivot point 41 thereby tending to raise the release which will in turn disengage inforced resin is atlixed to backing member 18 by fasten- 9 ing means 28. The hood 27 (FIGS. 2 and 3) comprises two elongated side portions 29 and a top arcuate cover portion 30 thereinbetween. A portion of cover 30 is slotted at 31 to allow the latch 22 to travel therein. The extent of upward latch travel in the slot 31 is limited by stop 22 on latch 22 which impinges upon a portion of member 19. The area of cover 30 defining the slot 31 limits sideways travel of the latch 22 andther'efore serves as a latch guide. The area 30' of cover 30 on either side of the lower extremity of slot 31 serves to restrict upward movement of each of the contacts 21 since contact face 21" will abut thereon after limited upward or forward movement of the contacts. 9

A crosswise support member 32 extends between the elongated sides 29 in the lower portion of the hood 27. This support member 32 in addition to providing structural strength to the hood 27 serves as a stop for the contacts 21 and for the latch 22 and thereby restricts the inward travel of the contacts and the downward travel of the latch. Downward travel of the latch is limited by the yoke 24' impinging on the support member 32.

The protector hood 27 is preferably of ,a molded insulating plastic and in addition to providing the above motion limiting functions serves to protect the upper contacts 21 from damage during shipping'and from damage during operation of the cut out as well as serving as guide means when closing in the fuseholder 11.

The upper movable contact assembly 33 is preferably of non-ferrous cast construction and comprises a tubular body 34 which is tightly aflixed to the outer periphery of the fuse tube. The other end of the tubular body 34 may be closed by either a non-expendable cap 34 or an expendable cap which may be similar'to that described in the beforementioned Jepsen patent. Within the upper bore of the tubular member a membersimilar to that described in the co-pending application, Serial No. 32,977, of Raymond J. Bronikowski entitled Fuse Construction and filed on May 31, 1960, may bepositioned although this is not shown. A laterally extending portion 35 of upper movable contact 33 has at its outer end an enlarged contact face 36 which is chamfered at the top 38 and bottom 37. As can be seen the actual contact face 36 is slightly arcuate in nature. 9

The particular configuration of latch face 25 and contact face area 3638 provides for ease in lifting the latch preparatory to latching lip 26 engaging the locking shoulder 39 of upper movable contact 33. It is particularly pointed out that if a fuseholder is closed in on a fault only a small upper area 38 of the contact face 36 initially comes in touching relation with the latch face 25 and therefore pitting and burning of actual contact lip 26 and shoulder 39. With the above in mind it is obvious that shapes of pull rings other than that shown will suffice equally well but these are not shown.

The lower movable contact assembly 43 (FIGS. 2 and 4) comprises a collar member 44 having an aperture 44 therein for receiving the fuse tube. A pin 45 joins the fuse tube and member 44 together and is placed on the compression side of the tube so that no weakening 0c face 36 will be virtually nil. Since initial contact is made stops 55 whose operation will be explained later.

curs on the tension side of the tube as a result of ma terial removal.

The underside 46 of member 44 is continuous and prevents gases expelled at the lower end of the tube from blowing or being blown upwardly and arcing over the exterior of the tube. A downwardly extending lip 47 projects substantially at right angles from the underside 46 of member 44 and has for one of its purposes the downward deflection of expelled gases to thereby decrease the tendency toward external tube fiashover. Substantially in alignment with tube and on either side of the upper portion of member 44 are two diamond'shapcd One side of member 44 at 48 may be cut away and a triangular recess 49 created which extends inwardly from the portion 48 to an area in the vicinity of the tens-ion side of the tube.

Pivotally attached to mebmer 44 as by pin 50 is a hinge contact member 51 having side portions 52 and portion 53 thereinbetween. At the top of hinge 51 and on either side of same above pin 50 are shoulder portions 54 which are adapted to impinge on stops 55 on member 44 thereby limiting relative movement between fuse tube and hinge 51. At the bottom of hinge member 5-1 are two rearwardly extending cam-like contact members 56 and a half-moon shaped trunnion 57 which projects laterally from the lower end of each of the sides 52. Also extending laterally from the sides 52 of the hinge member 51 are two relatively elongate rib portions 59 which have as their function the centering of the fuse tube during insertion of the tube into circuit bridging position.

A terminal thumb screw assembly 60 which affixes the end of a fuse link 11 to portion 53 of hinge 51 extends through portion 53 and is normally received in the recessed portion 49 of member 44.

A pivot pin 61 (FIG. 4) extends through trunnions on member 44. When the lever 62 begins to withdraw a ruptured fuse link leader from the fuse tube the interaction of lip 47 and shoulder 66 will delay relative movement between fuse tube and hinge 51 for a short time force to latch 22 when acted upon by a downward pull,

thereby unlatching lip 26 and shoulder 39. A spring 42 normally biases member 40 into touching relation with interval until lip 47 and shoulder 66 disengage. It is noteworthy that the only tensile force exerted on the fuse link 11' is a result of the spring 62'. Hence there 7 cut upon the spring 62 acting through the pivotally mounted-link flip out lever 62.

The half moon trunnions 57 are adapted to be received in C-shaped bearing members 69 on either side of the lower support 70. Note that the configuration of the bearing'members 69 is such that when the trunnions '7 are inserted therein and rotated to a position where the fuse tube is in circuit bridging relation that the half moon trunnions become locked to the bearing members so that no relative motion other than rotation can occur therebetween. The support 70 is aflixed to the lower portion of the insulator 12 as by a U-bolt 71. A terminal clamping member 58 which may be similar to member is attached to support 70 and hasfor its purpose the connection and retention of line conductors but the latter are not shown.

Inwardly of both of the C-shaped bearing members 69 is a pair of lower resilient'stationary contacts 72 which are afiixed at one end by suitable means 72' to the inner side 73 of the support 70'and which have free ends 74.

Behind the free end 74 of contact 72 on the inner side 73 of support 70 is a shouldered portion 75 which serves to limit the inward travel of the spring contacts 72.

Fixedly attached to that side of insulator 12 most removed from the fuseholder 11 is a hanger 77 (FIG. 1). The attaching means between hanger 77 and insulator may be a thru bolt 77' similar to bolt 15 but extending in from the other side of the insulator or an equivalent means such as an insulator U-bolt (not shown). The hangar has two outwardly flared portions 78 and a yoke portion 79 thereinbetween for engaging spaced apart portions of the periphery of the insulator 12. Reinforcing ribs 80 extend on both sides of an intermediate web portion 81 and decrease in height as they extend from the insulator.

An elongate L-shaped mounting bracket 13 has one leg affixed to the free end of hanger 77 and the other leg 84 affixed as by nuts and bolts 85 or other means to a crossarm 36. A second member 87 is positioned on the other side of crossarm 86 and is biasedinwardly by means 85. The hanger 77 and elongate mounting bracket 13 are so interconnected that the fuse cutout assembly is tilted at an angle to the vertical. This allows hot gases issuing from the tube to be directed away from the lineman if he happens to close in against a fault. The mounting bracket 13 is designed to have:

(1) High shock absorption,

(2) Relatively high deflection under heavy loads, and

(3) A low tendency for permanent setting under relatively heavy loads.

The fuse cutout assembly 16 is constructed so as to minimize the collisions between associated portions of the assembly and so as to provide a structure which moves substantially as an integral mass relative to the mounting bracket under the impetus of fuseholder thrust. The opertaion of the assembly in accomplishing this and other improved modes of operation will now be explained.

The fuseholder 11 may be assembled to the rest of the assembly 10 by inserting half-moon trunnions 57 on hinge 51 into bearing members 69. Because of the C- shape of the bearing members 69 and the half-moon configuration of trunnions 57 this must be done from an inverted fuse tube position, i.e., during insertion in the bearing members the top of the fuse tube must be below the bottom of the tube.

The fuseholder 11 is then rotated (as by a hook stick (not shown) engaging pull ring in the bearing members 62 as a unitary assembly due to the fact that fuse link 11' serves to keep shoulder 66 on flipout lever 62.

in engagement with lip 47 on member 44. Note in this connection that the ribs 59 on hinge member 51 will bear against surfaces 73 during closing in of the fuse tube thus- 22 to move upwardly around its pivot point. (If the line is faulted arcing will occur between the chamfered portion 38 of face 36 and the face 25 of latch 22 rather than between the contact face 21" of the upper stationary contacts 21 and the face portion 36.) Assuming that the line is not faulted at this time, as rotation of the tube continues, face 36 engages stationary contact faces 21", and portion 26 of latch 22 engages portion 39 of movable contact 33 in positive locking engagement. In this position the fuseholder 11 is in circuit bridging position.

When, for example, a fault current occurs and the fusble portion of link 11' ruptures as a result of this condition, gases will be evolved in the tube and venting from first one end and perhaps a little later from the other end of the fuse tube will take place. When the link ruptures link extractor 62 rotates in a clockwise direction under the impetus of its spring and removes a portion of the link 11 from the fuse tube (FIG. 5). Due to the rotation of extractor 62 shoulder 66 and lip 47 on member 44 disengage and the fuseholder 11 drops downwardly out of engagement with the latch and upper contacts until stops 55 on member 44 engages shoulder portions 54 on hinge 51. Then since the weight of the fuse tube and associated members is oif center it will pivot clockwise l (relative to FIG. 5) in the bearing members 65) until a portion of member 44 in the vicinity of pin 45 contacts a portion of support member 70- thusly preventing the tube from crashing into the insulator 12. Note that cam surfaces 56 and spring contacts 72 are so designed as to engage at a point above pivot point 57 so as to provide a moment helping to swing the fuse tube out of circuit bridging position subsequent to link ruptur and circuit interruption.

Due to the fact that a large amount of gas is generated by the fuse tube in interrupting high fault currents a substantial force is exertedon the fuse tube as these gases are vented. A number of features of the device 'limit or substantially prevent relative motion between associated parts of the assembly thusly insuring that the insulator, contact supports and fuseholder move as a substantially unitary mass under the impetus of the thrust forces developed as a result of gas venting.

The action of shoulder 66 on extractor 62 and lip 47 on member 44 normally prevent relative movement be-.

tween the fuse tube and binge member 51 until the fuse link 11' ruptures. The locking action of half-moon trunnions 57 in bearing members 69 positively prevents axial movement of the fuseholder relative to the Sta-- fuseholder movement in the same manner as crosswise member 32.

It is to be noted that on high fault currents (single vented operation) and consequently higher degrees of thrust forces that the fuseholder may impart a hammer like blow to the latch 22 causing it to travel upwardlyin the slot 31. Since the latch is relatively light (small mass) and spring 23 is relatively strong, the latch will tend to remain in engagement and follow the upward and downward motion of contact 33 and retain relative locking engagement with it. Upward movement of the latch is limited, as explained, by the action of members 19 and 22'. Note that the movement of the latch is occasioned by a hammer like. blow exerted by the fuseholder 11. This action is a result of the taking up of tolerances and the give experienced by various portions of the assembly. a

Thusly it canbe'seen'that motion between associated parts of the assembly is limited and that the effect of thrust forces will largely be transferred to, and dissipated in, the L-sh'aped mounting bracket 13 which is readily and expressly designed to absorb these forces.

It can thuslv be seen that our invention provides a fuse cutout wherein relative movement between portions thereof is kept to a minimum. The practical advantage of providing a fuse cutout which constitutes a substantially unitary mass will now be discussed from the point of view of the physical effects produced during single vented operation. (Single vented operation only is discussed since under proper double venting the unbalanced thrust is too small to be significant in cutout design). The following discussion will also involve the comparison ofa unitary mass cutout and a cutout which permits free movement of associated parts thereof relative to one another in order to better bring out the underlying concept of this invention.

During cutout operation an impulse is produced which is the product of the average thrust force (P) at a time duration (t). which is the product. of a mass (M) acted upon by the force (P) and the velocity (V) of such mass.

Let

M =mass of a fuseholder not in accordance with this invention wherein substantial relative movement between cutout components takes place and let M =mass of the fuseholder plus insulator and mounting'in'accordance with this invention KE =V2M V (energy, of movement to be dissipated) 7 Pt: M V KE,,= /2M V (energy of movement to be dissipated) Pt=Pt (assume constant thrust condition for both devices I M V =M V (note that V is normally much lessthan V since M is several times greater M (6) V,,= (solving for V (7) Substituting in (4) I 1 I M V, 1 M f KE,- Me M V. s) Subtracting (8) from (2) 1 M.-M; KE f-KE. M.Vf

Thusly it can be seen that Equation 9 represents the excess of kinetic energycreated by travel of the fuseholder which must eventually be absorbed by some portion of the'fuse mounting assembly if no provision is made for preventing substantial relative motion between fuseholder and mounting.

Note that Equation 8 represents the amount of energy that must be dissipated by a damped oscillation of the cutout. mounting bracket structure. It also represents the amount of kinetic energy developed when fuseholder and mounting move as a unitary mass.

Our invention in practice as well as theory results in a fuse cutout assembly that is not subject to damage resulting from high impact collisions of component parts thereof and which results in a structure wherein substantially all of the thrust force action on the assembly is absorbed in moving the substantially unitary mass and in temporarily or elastically deforming the mounting bracket.

It is entirely Within the spirit of this invention to utilize the construction shown and basic principal involved in an enclosed type cutout although this is not shown in order to shorten the disclosure and to facilitate the un derstanding thereof. It is also to be understood that the fuseholder of this invention may be substituted for by a switch blade to achieve a disconnect switch.

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 in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

This impulse produces a momentum 7 We claim:

1. In a fuse cutout assembly of the type comprising a mounting bracket, an insulating member mounted thereon, an upper terminal contact assembly mounted on one end of said insulating member, fuseholder supporting means fixedly mounted on the other end of said insulating member, lower terminal contact means aifixed to said support means, and a fuseholder assembly comprising a gas evolving fuse tube with a rupturable fuse link therewithin and an upper contact member and a lower contact assembly mounted at opposite ends thereof respectively for engagement with said upper terminal contact assem bly and said lower terminal contact means; the improvement comprising, said upperterminal contact assembly and said upper contact member comprising respectively, resilient stationary contact means, downwardly biased latch means mounted on said insulating member, means aifxed to said insulating member for limiting movement of said resilient contact means and said latch means, and an upper movable contact member normally engaging said resilient contact means and having a portion thereof engageable with a portion of said latch means to retain engagement of said resilient contact means and said upper contact member, said resilient contact means further characterized by being operable to bias said upper contact member into engagement with said latch means, in combination with said lower terminal contact means and said lower contact assembly, said lower terminal contact means comprising resilient contacts and means for limiting movement of said resilient contacts, and said lower contact assembly comprising, means aflixed to said I fuse tube, cam contact means pivotally mounted on said means afiixed to said fuse tube and engageable with said resilient contacts, trunnion means associated with said cam contact means and'receivable in said fuseholder supporting means in such a manner that axial movement of said fuseholder is substantially prevented, link flip means associated with said cam contact means and pivotally movable with respect thereto and engageable with a portion of said means aflixed to said fuse tube to normally prevent relative motion between said cam contact means and said fuse tube, and means for limiting pivotal movement of said cam contacts with respect to said fuse tube, whereby duringcurrent interruption of the type accompanied by unbalanced thrust forces said fuse cutout assembly moves substantially as a unitary mass, the energy so generated being dissipated in said mounting bracket.

2. In a fuse cutout assembly of the type having a mounting bracket, an insulating member mounted thereon, a terminal contact assembly affixed to one end of said insulating member, fuseholder supporting means aflixed to the other end of said insulating member, terminal contact means mounted on said fuseholder supporting means, and a fuseholder assembly comprising a fuse tube and a contact member and a contact assembly mounted at opposite ends of said fuse tube and engageable with said terminal contact assembly and said terminal contact means respectively; said terminal contact assembly and said contact member comprising respectively, contact means, latch means mounted on said insulating member, means for limiting movement of said contact means and said latch means, said contact member being constructed and arranged to engage said contact means and having a portion thereof engageable with said latch means to retain engagement of said contact means and saidcontact mem-' her, said contact means being operable .to normallyv bias said contact member into engagement with said latch means, in combination with said terminal contactmeans and said contact assembly, said terminal contact means comprising lower contacts and means for limiting travel of said contacts, and said contact assembly comprising, means fixedly attached to said fuse tube, contact means pivotally mounted with respect to said means atfixed to said fuse tube and engageable with said lower contacts, trunnion means associated with said pivotally mounted contact means and engageable with said fuseholder supporting means to substantially prevent axial movement of said fuse tube, link flip out means associated with said pivotally mounted contact means and pivotable with respect thereto, said flip out means being engageable with a portion of said means med to said fuse tube to normally prevent relative motion between said pivotally mounted contact means and said fuse tube, and means afiixed to said means afiixed to said fuse tube for limiting pivotal movement of said pivotally mounted contact means with respect to said fuse tube, whereby thrust forces developed during current interruption by said fuse cutout assembly serve to move said cutout as a substantially unitary mass with respect to said mounting bracket, the kinetic energy so developed being substantially dissipated in said mounting bracket.

3. In a fuse cutout assembly of the general type having a mounting bracket, an insulating member aflixed intermediate its ends to said mounting bracket, an upper terminal assembly attached to one end of said insulating member, fuseholder supporting means attached to the other end of said insulating member, lower terminal contacts afiixed to said supporting means, a fuseholder assembly comprising a gas evolving fuse tube having a rupturable fuse link therewithin and an upper fuse tube contact and a lower fuse tube contact assembly; the improvement therein comprising, said upper terminal assembly having, at least two spaced apart resilient contacts, a spring biased latch member pivotable with respect tosaid insulator and extending between said spaced apart contacts, means fixedly attached to said insulator for limiting travel of said resilient contacts and said latch member, said upper fuse tube contact having a contact face engageable with each of said spaced apart contacts and a portion engageable with a portion of saidlateh member to retain contact between said resilient contacts and said fuse tube contact, wherein said resilient contacts normally urge said fuse tube contact and said latch into engagement with one another, in combination with, lower resilient terminal contacts, means for limiting movement of said resilient terminal contacts, and a fuse tube contact assembly comprising collar means aflixed to said fuse tube, cam contacts pivotally mounted on said collar means and engageable with said lower resilient terminal contacts, means for limiting pivotal movement of said cam contacts with respect to said fuse tube, trunnion means associated with said cam contacts and engageable with said fuseholder supporting means to prevent axial movement of said fuse tube with respect to said supporting means, pivotal means mounted on said cam contact means and normally engaging said collar means to prevent relative movement between-said cam contacts and said fuse tube, wherebysaid fuseholder assembly and said insulator move substantially as a unitary'mass under the impetus ofunbalaneed thrust forces developed on the fuse tube during circuit interruption, the kinetic energy so developed being substantially dissipated in said mounting bracket.

4; In a fuse cutout assembly of the general type having, a mounting bracket, an insulating member aflixed intermediate its ends to said mounting bracket, an upper terminal assembly attached to one end of said insulating member, fuseholder supporting means attached to the other 'endzof said insulating member, lower terminal contacts affixed to said fuseholder supporting means, a fuseholder assembly comprising a gas evolving fuse tube having a rupturable fuse link therewithin and an upper fuse tube contact and a lower fuse tube contact assembly; the improvement therein comprising, said upper terminal assembly having resilient contact means, spring biased latch means movable with respect to said insulator, means afiixed to said insulator for limiting movement of said resilient contact means and said latch means, and said upper fuse tube contact being engageable with said resilient contact means and said latch means wherein said resilient contact means normally urges said upper fuse tube contact into locking engagement with said latch means, in combination with, lower resilient spaced apart contacts having a free end, means integral with said fuseholder supporting means for limiting movement of said resilient spaced apart contacts, and a fuse tube contact assembly comprising, collar means afiixed in embracing relation to said fuse tube, hinge means pivotally attached to said collar means, stop means integral with said collar means for limiting relative movement between said collar means and said hinge means, trunnion means integral with said hinge means and receivable in said fuseholder supporting means to normally prevent axial movement-of said fuse tube with respect to said fuseholder supporting means, cam contact surfaces integral with saidhinge means and normally in engagement with each of said lower spaced apart resilient contacts, link flip outmeans pivotally mounted on said hinge means and normally engaging a portion of said collar means to prevent relative movement between said hinge means and said fuse-tube, whereby upon unbalanced thrust force development on said fuse tube incident to current interruption said complete fuse cutout assembly moves as a substantially unitary mass, the energy so developed being dissipated in said mounting bracket.

References Cited in the file of this patent UNITED STATES PATENTS 2,109,090 Pittman et al Feb. 22, 1938 2,230,955 Johnson Feb. 4, 1941 2,328,818 Lindell et al Sept. 7, 1943 2,365,113 Schultz Dec. 12, 1944 2,400,850 Steinmayer et al May 21, 1946 2,403,121 Rawlins et al July 2, 1946 2,484,839 Lindell Oct. 18, 1949 2,843,704 Wood July 15, 1958 2,853,581 Olive Sept. 23, 1958