US2836678A - Fuse cutout construction - Google Patents

Description

y 7, 5 A. G. BALE, JR 2,836,678

FUSE CUTOUT CONSTRUCTION Filed June 21, 1955 2 Sheets-Sheet 1 INVENTOR.

BY I

ATTOR/V'Y May 27, 1958 A. G. BALE, JR

FUSE CUTOUT CONSTRUCTION Filed June 21, 1955 2 Sheets-Sheet 2 [N V EN TOR.

ATTORNEY United States Patent FUSE CUTOUT CONSTRUCTION Alton G. Bale, In, South Milwaukee, Wis., assignor to McGraw-Edison Company, a corporation of Delaware Application June 21, 1955, Serial No. 516,917

8 Claims. (Cl. 200-114) The present invention relates to a fuse cutout construction, and particularly relates to a cutout characterized by its ability to safely close an electric circuit even though fault conditions may exist thereon.

When a fault condition develops on a distribution circuit causing the fusible element of a fuse cutout to rupture, large mechanical forces may develop in the cutout. Conventional housed cutouts are constructed with sufficient strength to counteract any expulsive forces caused by rupture of the fuse link when all of the cooperating members are in secure mechanical engagement relative to one another. This is true even in the relatively confined space provided in conventional cutout housings. However, when an attempt is made to reclose conven tional cutouts after replacement of a ruptured fuse link,

and on the existence of a low impedance fault, violent arcing between contacts often occurs with consequent profuse evolution of hot gases. Inasmuch as the gases are relatively confined, they will act immediately to force an incompletely closed cutout dooropen with such violence as to injure or burn a lineman servicing the fuse. In many cases, there is even the'possibility of the porcelain housing' being blown apart by the evolution of relatively confinedgases.

It is, therefore, a primary'obje ct of the present invention to provide a fuse cutout construction which will permit the cutout to be'reclosed to complete the electric circuit even though a fault condition may persist without risk to operating personnel.

It is another object of the present invention to provide a fuse cutout construction which permits secure mechanical engagement of all cooperating members prior to release of an auxiliary switch for completing the circuit through the protective fusible element.

It is a further object of this invention to provide a fuse cutout construction adapted to permit the nearly r complete mechanical closure of its mating terminal members prior to the initiation of electrical circuit continuity through the terminals and their bridging fusible element.

An embodiment of the invention is shown in the accompanying drawings, in which:

Fig. 1 is a sideelevational view, in section, showing an embodiment of the fuse cutout in conjunction with an insulating cutout box, the fuse cartridge assembly being shown in non-conductive position;

Fig. 2 is a fragmentary sectional view of the fuse illustrated in Fig. 1, after all of the cooperating parts are in complete registration and mechanical seeurement relative to one another, and after the movable auxiliary contact has been tripped to conductive position;

Fig. 3 is a cross sectional view taken along lines 3-3 of Fig. 1.

Referring to Fig. 1 of the drawing, it will be seen that the fuse cutout comprises an insulating housing 1 which is supported on a metallic bracket 2 and an insulatingdoor 3 having a manipulating eyelet, or handle 4.

The door is hingedly' supported on the housing 1 by means of trunnions 5 which extend laterally from the 2,836,678 Patented May 27, 1958 ice lower edge of the door and are removably seated within the spaced apart, hook-like portions of a rigid bracket 6. The door 3 is adapted to pivot into closed position with relation to the housing 1, and to be removed from the bracket 6 for maintenance operations or replacement of ruptured fuse links.

It will be seen, with reference to Figs. 1 and 2, that the insulating door 3 fixedly carries on it a fuse cartridge assembly, indicated generally by the reference numeral 10. When the door 3 isclosed with respect to housing 1, as illustrated in Fig. 2, the upper terminal cap 11 of the cartridge 10 contacts and becomes electrically engaged with an upper stationary resilient contact 12 affixed within the housing in electrical association with a pair of U-shaped yieldable terminal clips 13 which serve to guide the cap 11 into alignment with the contact 12. Members 12 and 13 are connected to an incoming electric line conductor (not shown) by means of a screw type connector 14. The entire stationary terminal assembly may be cemented to the porcelain box 1 as shown, or mounted by any suitable, well-known means.

The cartridge 10 is connected to an outgoing line conductor (not shown) through the medium of a connector 29 at the lower portion of the housing 1. The circuit is completed from the connector to a lower terminal in the form of a U-shaped yieldable clip 21, and is anchored thereon by means of a machine screw 22.

When the door 3 is swung to closed position, as shown in Fig. 2, lower stationary terminal clips 21 are adapted to electrically slidably receive therebetween a conductive contact denoted generally by the numeral 23, which in turn, supports the cartridge assembly it). The lower fuse contact 23 is rigidly affixed to the door by means of machine screws 24 to prevent the cartridge assembly 11) from sliding with respect to the lower contact 23. To further secure the cartridge from sliding axially relative to the contact 23 a transverse pin 25 is driven through the contact and engages the outer peripheral wall of the fuse tube 26.

The fuse tube 26 is also embraced adjacent its lower end by a forked plate 28 which is attached by means of screws 29 to a rigid conductive appendage 30 extending from and cast integrally with the lower fuse tube contact 23. It is preferable to insert a soft rubber sleeve 31 between the forked plate 28 in the fuse tube 26 to provide a gas barrier to" prevent flashover between the spacedapart terminals during normal interruption of the fuse link.

As will be evident from Fig. 1, the lower extremity of appendage 30 pivotally supports a fuse link throw-out lever 35 by means of a pivot pin 36. Circumjacent to the pivot pin is a torsion coil spring (not shown) which acts to bias the throw-out lever 35 in clockwise direction. The lever 35 engages a flexible conductive fuse link leader extending from the lower end of the fuse tube 26 in order to normally urge the leader towards removal from the fuse tube. The free end of the leader is brought back and around a threaded stud 41 staked to the appendage 30 and to which the leader is electrically connected by means of a knurled thumb screw 42. Thus, it will be apparent that electrical continuity is established from the cartridge assembly 10 to the outgoing line terminal 20 through an intermediate path comprising the p ,be mounted on any standard insulating fuse cutout door '3. Essentially, the cartridge comprises a tube 26 of any hard insulating material, such as that sold under the is recessed to provide the integral protruding pad 53 positioned in the upper bore 54 of theshell 50. The member 52 may be of insulating material (not shown) or may be insulated from the outer terminal cap 11 by the injected molded insulating material 55 positioned therebetween. The pad 53 is adapted to engage the buttonhead 60 of a fuse link when the member 52 is threaded downwardly on the portion 51 of the shell This assures positive electrical engagement between the buttonhead 6t and the internal shoulder portion 61 of the conductive shell 59. In addition to providing secure electrical contact, the button 60 acts as a closure to prevent the hot gases which accompany rupture of the fusible element 62 from escaping upwardly above the button; however, the hot gases and fuse flexible leader are ejectable from the lower end of the fuse tube 26.

The complete removal of the leader after rupture is assisted by the action of the spring biased fuse link throw-out lever 35.

The auxiliary contact assembly comprises the terminal cap 11 which acts as a stationary contact member, when in electrically engaged position with the contact 12. The cap 11 preferably includes an outwardly flanged arcing tip 56 of a conductive material, such as a copper-tungsten material, capable of resisting any arcs during circuit closing movement. The movable auxiliary contact comprises the resilient conducting cup-like member 70 having circumferentially spaced longitudinal slits 71 to provide a plurality of resilient contact fingers. As shown in Fig. 1, the movable auxiliary contact 70 is in loaded or cocked position prior to release towards conducting position relative to the terminal cap 11. The contact member 70 is preferably provided with arcing tips 72 of the heretofore mentioned arc resisting material. The movable contact 70 is maintained in ready position by means of the inwardly bent spring fingers 73 which are received in a cooperating annular retaining groove 74 (see Fig. 2) provided in the outer periphery of the shell 50. movable auxiliary contact member 70 is normally urged towards movement in an axial direction towards the terminal cap 11 by means of the circumjacent coilspring &

75. The Washer 76 attached to the shell at its lower end provides an upper bearing surface for the spring 75, and the retaining ring 77 seated in the tube 26 provides the lower bearing surface for the opposite end of the spring.

As shown in Fig. 1, the door 3 has been moved towards closure with the insulating housing 1 with the conductive terminal cap 11 initially engaging the resilient stationary contact 12. It will be apparent that the electrical engagement between the cooperating members is relatively insecure when compared to the full closure of the door as shown in Fig. 2.

Referring now to Fig. 3, it will be seen that the movable auxiliary contact member is provided with laterally extending cradle-like cam follower members 80. The members 80 are adapted to slidably engage an integrally formed U-shaped cam surface 81 of the housing 1. The surface 81 is angularly disposed relative to the housing 1 and permits the followers 80 to ride on the incline to a position wherein the spring fingers73 will be forcibly released from the angular retaining groove 74 to'permit the spring to urge the movable auxiliary contact 50 to freely slide upwardly and engage the contact arcing.

tips 56 of the terminal cap 11 and complete; the elec: trical circuit. This positionis shown in Fig. 2 with the The aux-iliary contacts being, in closed. electrical position. It will now be seen that the electrical circuit through the fuse cartridge is completed from the-upper terminal con tact 12 to the cap 11 through the contact tips 56 and 72 to the conductive shell 50, the buttonhead 60 and through the fusible element 62 to the leader 40. The remaining portion of the circuit has heretofore been described.

Although the auxiliary contact tripping means has been shown here as an inclined plane cam with cooperating follower, it will be apparent that auxiliary contacts may provided with other retaining devices and cooperating tripping means, not shown. The tripping action may be executed by means of a leverage arrangement communicating from outside a securely closed door (not shown) or by inserting trip members in the housing by conventional cementing operations. The auxiliary contacts, themselves may also take other forms than the preferred arrangement illustrated herein without departing from the scope of the present invention.

It will be obvious that the cam surface 81 may be inclined as. desired to provide a preferred closure relationship prior to electrical engagement of the auxiliary contacts. As shown in the present embodiment, the door 3 will be nearly closed mechanically before the fingers 73 will be forced from the groove 74 to permit release of the movable auxiliary contact 70 towards electrical engagement. The remaining amount of mechanical closure will have been completed in the time that it takes the fusible element 62 to melt should an overcurrent condition exist.

As far as the operation of the device is concerned, it will be apparent from the above description that mechanical closure of the device is substantially completed prior to automatic circuit closure provided by means of the tripping cam surface 81 acting through the cam follower.

to actuate the auxiliary contacts towards engagement with one another. The device may remain in operating position as shown in Fig. 2, or the door 3 may be removed after closure for temporarily testing the power line for. still-existing faults. If the element 62 is not immediately ruptured on complete closure of the door 3, the door may be removed and a conventional cartridge door assembly (not shown) may be reinserted in its place.

On rupture of the fuse link element 62, the door is,

opened and removed from the bracket 6 for re-fusing,

This is accomplished by unscrewing the terminal capes, sembly from the threaded reduced portion 51 of the shell.

50 and removing the buttonhead portion 60. The ejected leader portion 40 isthen removed from the post 41 by unscrewing the thumb screw 42. The cup-like contact"70 may be moved to cocked position with the spring fingers:-

73 being seated in the retaining groove 74 either after, but preferably before, the cap 11 is removed from the shell 50. A new fuse link is insertedthrough the bore of the fuse tube 26 with the buttonhead 60 resting on the shoulder 61 of the shell 50. The cap 11 is then screwed in place. The lever 35 is next brought into biased position as shown in Fig. 1 with the leader 40 resting thereon. The leader is then fastened to the conducting post 41 by means of the screw 42 and any extending portions clipped off with conventional side cutter pliers. The unit is now ready for operation.

It will be noted that the present invention provides anovel safety fuse cutout assembly which may be operated to closed circuit position without danger to operating personnel, and wherein premature uncontrolled arcing is precluded. Moreover, it will be noted that the construction is such as to conclude a minimum amount of moving parts, and is rugged, highly simplified andeconomical.

I claim:

1. In combination with a fuse cutout having spacedline terminals, a movable fuse cartridge assembly arranged to mechanically bridge said line terminals and containing a fusible element adapted to. electrically bridge saidter minals comprising auxiliary contacts normally spaced from each other and arranged for relative movement towards one another to complete the electrical bridging circuit through said fusible element, biasing means urging said contacts toward said relative movement, latch means normally restraining said contacts in spaced relation prior to mechanical bridging of said terminals by said fuse cartridge, and means cooperating with said latch means for releasing said contacts into conductive relation to complete said current path through said fusible element after said terminals have been positively mechanically bridged by said fuse cartridge.

2. In combination with a fuse cutout having spaced line terminals positioned within an insulating housing, a door assembly having positioned thereon a fuse cartridge for electrically bridging said terminals, said cartridge having a current path therethrough-including contacts normally spaced from each other, biasing means urging said contacts toward each other, latch means restraining said contacts in spaced relation prior to bridging of said terminals by said fuse cartridge, and latch trip means internally of said housing engageable with said latch means for releasing said contacts into conductive relation on movement of said fuse cartridge and door to a predetermined closure position and after said terminals have been positively mechanically bridged by said fuse cartridge.

3. A fuse cutout assembly including in combination an insulating housing including therein a pair of spaced apart line terminals, a door assembly for said housing having rigidly secured thereto a fuse cartridge assembly for electrically and mechanically bridging said line terminals, said cartridge assembly comprising an insulating fuse tube open at one end and closed at the other end, a stationary conductive member positioned at the said other end of said fuse tube, a fuse link positioned in the bore of said fuse tube and electrically engaging said conducfive member, a conductive terminal contact on said fuse tube electrically engageable with one of said line terminals and mounted in normal insulating relationship relative to said stationary conductive member, a movable contact adapted to electrically bridge said terminal contact and said conductive member on movement thereof, temporary latch means for restraining movement of said movable contact, biasing means normally urging said movable contact from temporary restrained position and towards electrical bridging position, and latch trip means adapted to release said latch means to permit said movable contact to electrically bridge said terminal contact and said conductive member after said door has been moved to a predetermined closure position, and with the said fuse cartridge positively mechanically bridging said spaced apart line terminals.

4. A fuse cutout assembly including in combination an insulating housing including therein a pair of spaced apart line terminals, a door assembly for said housing having rigidly secured thereto a fuse cartridge assembly for electrically and mechanically bridging said line terminals, said cartridge assembly comprising an insulating fuse tube open at one end and closed at the other end, a conductive shell exteriorly of said fuse tube, a fuse link positioned in the bore of said fuse tube and electrically engaging said conductive member, a conductive terminal contact electrically engageable with one of said line terminals and mounted in normal insulating relationship relative to said conductive member, a movable contact axially slidable relative to said conductive member and arranged to electrically bridge said terminal contact and said conductive member on axial movement thereof, temporary latch means for restraining movement of said movable contact, a coil spring circumjacent said tube and normally urging said movable contact in an axial direction from temporary restrained position and towards electrical bridging posi tion, and latch trip means comprising an inclined cam surface integral with said housing and a cam follower slidably engageable therewith and forming an integral part of said movable contact, said trip means adapted to forcibly release said movable contact from temporary restrained position to bridging position after said door has been moved to a predetermined closure position, and with the said fuse cartridge positively mechanically bridging said spaced apart line terminals.

5. A fuse cutout assembly including in combination an insulating housing including therein a pair of spaced apart line terminals, a door assembly for said housing having rigidly secured thereto a fuse cartridge assembly for electrically andmechanically bridging said line terminals, said cartridge assembly comprising an insulating fusetube open at one end and partially closed at the other end by means of an inwardly extending apertured shouldered portion of a conductive shell mounted on the said other end, a fuse link positioned in the bore of said fuse tube threaded through said apertured shouldered portion and having a buttonhead electrically engaging said shouldered portion and completing the closure of said other end of said fuse tube, a conductive terminal contact electrically engageable with one of said line terminals and mounted in normal insulating relationship relative to said shell, a movable contact axially slidable relative to said shell and in electrical contact therewith, biasing spring means normally urging said movable contact towards engagement with said terminal cap, temporary latch means normally restraining axial movement of said movable contact and comprising resilient inwardly biased latch fingers on said contact normally engageable With an annular groove in the outer periphery of said shell, and latch trip means, adapted to release said movable contact from said temporary latch means to slidably move towards electrical engagement with said terminal contact after movement of said door assembly to a predetermined closure position, and with the said fuse cartridge positively mechanically bridging said spaced apart line terminals.

6. A fuse cutout assembly including in combination an insulating housing including therein a pair of spaced apart line terminals, a door assembly for said housing having rigidly secured thereto a fuse cartridge assembly for electrically and mechanically bridging said line terminals, said cartridge assembly comprising an insulating fuse tube open at one end and partially closed at the other end by means of an inwardly extending apertured shouldered portion of a conductive shell mounted on the said other end, a fuse link positioned in the bore of said fuse tube threaded through said apertured shouldered portion and having a buttonhead electrically engaging said shouldered portion and completing the closure of said other end of said fuse tube, a conductive terminal cap electrically engageable with one of said line terminals and mounted in normal insulating relationship relative to said shell, a movable contact axially slidable relative to said shell and in electrical contact therewith, biasing spring means normally urging said movable contact towards engagement with said terminal cap, temporary latch means normally restraining axial movement of said movable contact and comprising resilient inwardly biased latch fingers on said contact normally engageable with an annular groove in the outer periphery of said shell, and latch trip means comprising an inclined cam surface integral with said housing and a cam follower slidably engageable therewith and forming an integral part of said movable contact, said trip means adapted to forcibly relese said latch fingers from said annular groove to permit electrical engagement of said contact with said terminal cap after said door has been moved to a predetermined closure position, and with the said fuse cartridge positively mechanically bridging said spaced apart line terminals.

7. In combination with a fuse cutout having spaced line terminals positioned within an insulating housing, a closure assembly having positioned thereon a fuse cartridge means for electrically bridging said terminals, said cartridge means having a current path therethrough it1 cluding contacts normally spaced from each other, biasing means urging said contacts toward each other, first means operable to restrain said contacts in spaced relation prior to bridging of said terminals by said fuse cartridge, and second means cooperable with said first means and operable to' effect movement of said contacts into conductive relation subsequent to movement of said fuse cartridge and closure assembly to a predetermined closure position and after said terminals have been positively mechanically bridged by said fuse cartridge.

8. In combination with a fuse cutout having spaced line terminals, movable fuse cartridge means for electrically bridging said terminals including auxiliary contacts normally spaced from each other, means urging said auxiliary contacts of said cartridge means toward each other, first means operable to maintain said contacts in spaced relation, and means cooperable with said first means and operable to effect movement of said auxiliary contacts into conductive relation subsequent to movement of said fuse cartridge means to a predetermined positive- References Cited in the file of this patent UNITED STATES PATENTS 826,888 Sachs July 24, 1906 974,106 Furbush Oct. 25, 1910 1,177,016 Cheney Mar. 28, 1916 1,348,208 Clay Aug. 3, 1920 1,535,636 Ullrich Apr. 28, 1925 1,556,829 Wyman Oct. 13, 1925 2,299,196 Wallace Oct. 20, 1942 2,438,746 Garrison Mar. 30, 1948 2,472,625 Smith June 7, 1949 2,617,908 Lincks Nov. 11, 1952 2,663,825 Amundson Dec. 22, 1953 2,677,738 Schneider May 4, 1954

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