US3377447A

US3377447A - Loadbreak for open type cutouts

Info

Publication number: US3377447A
Application number: US444166A
Authority: US
Inventors: Benjamin R Hermann; Robert E Koch
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1965-03-31
Filing date: 1965-03-31
Publication date: 1968-04-09
Anticipated expiration: 1985-04-09

Description

April 9, 1968 B. R. HERMANN ETAL 3,377,447

LOADBREAK FOR OPEN TYPE CUTOUTS Filed March 31, 1965 4 Sheets-Sheet l April 9, 1968 B. R. HERMANN ETAL 3,377,447 LOADBREAK FOR OPEN TYPE GUTOUTS Filed March 51, 1965 4 Sheets-Sheet 2 April 9, 1958 B. R. HERMANN ETAL 3,377,447

LOADBREAK FOR OPEN TYPE CUTOUTS Filed March 31, 1965 4 Sheets-Sheet 3 April 1968 B. R. HERMANN ETAL 3,377,447

LOADBREAK FOR OPEN TYPE CUTOUTS Filed March 31, 1965 4 Sheets-Sheet 4 fizz m5, 56/2 6202/72 1?. 19077707272,

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United States Patent 3,377,447 LOADBREAK FOR OPEN TYPE CUTOUTS Benjamin R. Hermann, Lanesborough, and Robert E. Koch, Pittsfield, Mass., assignors to General Electric Company, a corporation of New York Filed Mar. 31, 1965, Ser. No. 444,166 4 Claims. (Cl. 200-114) This invention relates to loadbreaks for open type cutouts and more particularly to improvements in the construction and operating mechanism thereof.

A cutout as this term is used in the electric power distribution art is a certain kind of circuit interrupter. Usually it is a renewable fuse device in which case it is called a fuse cutout. When the fuse or fuseholder is in the open air it is called an open type fuse cutout and when the fuse or fuseholder is in a housing it is called an enclosed type fuse cutout. A fuse, however, is not essential and there is a form of cutout known as a disconnecting cutout which is the functional equivalent of a disconnecting switch, and the structural equivalent of a fuse cutout except that the fuse is replaced by a simple switch blade. Both fuse cutouts and disconnecting cutouts can be used to interrupt or open a circuit which is not carrying load current and fuse cutouts can and, of course, are intended to interrupt overload currents. However, one thing that both fuse cutouts and disconnecting cutouts have in' common is that they are not suitable for interrupting load current like a circuit breaker.

A loadbreak as the term is used here is a load current interrupter attachment or tool for adapting a cutout to interrupt load current.

In application Ser. No. 440,186 filed Mar. 16, 1965 in the name of Sidney R. Smith, Jr., and assigned to the present assignee, there is disclosed and claimed a novel loadbreak for open type cutouts which is mounted on a pivoted latch release arm in order to obtain the desired operation or operating sequence during opening and closing operation.

In accordance with this invention, there is provided a loadbreak device which is an improvement on the one which is the subject matter of the above identified Smith application and which is rigidly rather than pivotally mounted on the cutout arm which carries one of the main contacts and improved auxiliary pivotally mounted nonarcing duty contact members are provided for more positively insuring the proper sequential actions during opening and closing of the cutout.

An object of the invention is to provide a novel and simple improved loadbreak device for open cutouts.

Another object of the invention is to provide a load break device for open type cutouts having improved reliability of operation.

The invention will be better understood from the fo1- lowing description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings,

FIG. 1 is a perspective view of a preferred embodi' ment of the invention mounted on an open type cutout,

FIG. 2 is an enlarged partly broken away detailed perspective view of the main contacts and latch assembly of the device shown in FIG. 1,

FIG. 3 is a side elevation view of the loadbreak de vice shown in FIG. 1,

FIG. 4 is an edge elevation view of the device shown in FIG. 3 when viewed from left to right,

FIG. 5 is an edge elevation view of the device shown in FIG. 3 when viewed from right to left,

FIG. 6 is a sectional view taken on line 6-6 of FIG. 3,

FIG. 7 is a detailed view of the segmental shaped movable arcing duty contact of the device shown in FIG. 3,

FIG. 8 is a view of the device shown in FIG. 3 with the top plate removed, i.e. a sectional view taken on line 8-8 of FIG. 6, showing the position of the parts in the arcing chamber during arc interruption,

FIG. 9 is an enlarged detailed partly broken away perspective view of the fixed arcing duty contact assembly at the upper right-hand corner of the device shown in FIG. 3,

FIG. 10 is a side elevation view of the device shown in FIG. 1 at the commencement of an opening stroke after the normally latched closed main contacts have been unlatched and separated,

FIG. 11 is a view generally similar to FIG. 10 showing the progressive sequence of operation during the opening stroke,

FIG. 12 illustrates the continued sequence of operation during the opening stroke to the final position when the movable cutout arm has been swung clear,

FIG. 13 shows an intermediate position of the device on a closing stroke, and

FIG. 14 shows the final sequence of operations on the closing stroke when the parts are returned to the position shown in FIG. 1.

Referring now to the drawings and more particularly to FIG. 1, there is shown therein an open type cutout designated generally by the reference numeral 1, and a loadbreak device designated generally by the reference numeral 2 mounted on the cutout. The cutout is shown as comprising a main frame having a Y-shaped support casting 3 into which are seated two generally similar flexible insulating arms 4, the free end of the upper one of 'which is attached to a latch casting 5 and the free end of the lower one of which is attached to a hook casting 6. Line terminals 7 are mounted or integrally formed with latch casting 5 and hook casting 6. The circuit between these line terminals 7 is completed through a pivotally mounted arm indicated generally by the reference numeral 8. This may either be a switch blade or, as shown, an insulating fuse tube 9 in which there is a conducting fuse and its integral connecting lead extending from a buttonhead (not shown) under a cap 10 through the lead 11 to a terminal 12 on a hinge casting 13 in which the lower end of the tube 9 is seated. The hinge casting 13 is provided with trunnions 14 seated in the hook casting 6 so that the arm 8 can be swung about a hinge or pivot axis through the trunnions 14. Good electrical connection between the hook casting 6 and the hinge casting 13 is provided by blade spring fingers 15 attached to the hook casting and pressing against the trunnions 14 of the hinge casting 13.

The details of the interrelationship of the latch casting 5 and the upper end of the arm 8 are shown in FIG. 2 to which reference will now be made. The upper end of the fuse tube 8 carries a conducting casting 16 and the latch casting 5 is provided with integral flaring guide cars 17 for guiding the casting 16 into a latched closed position. The casting 16 has a bumper stop 18 for engaging the latch casting 5 and limiting the inward movement of the casting 16. Below the bumper stop 18 is an integral moveable main contact 19 on the casting 16 which engages a fixed but sprung main contact 20 on the latch casting.

The contact 20 is most clearly shown in FIG. and it is connected to a spring metal strip 21 and a high conductivity strap 22 for carrying the current to the line terminal 7 on the latch casting 5. Referring again to FIG. 2, the casting 16 is also provided with integral opposite lateral extensions 23 having a rounded front side and a square corner rear side. The square corner rear side fits in a notch 24 in each guide ear 17 for latching the main contacts 19 and into engagement. A latch release lever 25 is pivotally attached at 26 to the casting 16. This lever is provided with an eye 27 for receiving the hook of a switch stick and its other end is bifurcated, the two parts thereof normally being below a shoulder 28 on the guide ear. Thus by pulling downwardly on the .eye 27 as viewed in the drawings the latch release lever 25 pivots so as to pry the latch and

hook castings

5 and 6 apart, which action is possible because of the resilience of the insulating arms 4. When the notches 24 clear the square rear corners of the projections 23, the latch is released and the arm 8 can be swung in a clockwise direction about the trunnions 14 for opening the main contacts. When it is desired to close the main contacts, the arm 8 is pivoted in the opposite direction about the trunnions 14, the rounded front ends of the projections 23 then engaging the bottom surfaces of the guide cars 17 and wedging the latch and

hook castings

5 and 6 apart enough to allow the lateral projections 23 to slip past the notches 24 in the guide cars 17. The

castings

5 and 6 then move toward each other and the main contacts are latched closed. The loadbreak device 2 is mechanically supported by and electrically connected to the casting 16 by a conductive bracket 29.

Also mounted on the latch casting 5 is a conductive bracket 30 provided with an integral stop portion 31 for a pivotally mounted non-arcing duty auxiliary contact 32 which is normally biased by means of a coil spring 33 against the stop 31. This mechanism, as well be described hereafter, cooperates with the loadbreak device 2. The

parts

32 and 33 are most clearly shown in FIG. 1.

The details of the loadbreak device 2 are most clearly illustrated in FIGS. 3 through 8. Referring first to FIG. 3, the loadbreak device is sector shaped having straight

radial sides

34 and 35, with a common center 36, and an opposite segmental side 37. Mounted at the junction of the radial side 34 and the segmental side 37 is a fixed arcing contact assembly 38, the details of which are most clearly shown in FIG. 9. Adjacent the other radial side is a drag arm 39 having a bifurcated end pivotally mounted on a pin 40 extending through the common center 36 of the radial sides. A coil spring 41 serves to bias the drag arm 39 against the radial side 35. Attached to the drag arm 39 intermediate its ends is a segment shaped arcing duty contact 42 shown most clearly in FIG. 7 which extends into an arcing chamber in the loadbreak device 2 and whose other or free end engages the fixed arcing duty contact in the assembly 38. The segment shaped contact 42 is provided with a lateral projection or hook 43 for engaging the radial side 35 and preventing withdrawal of that end of the contact 42 from the arcing chamber, this cooperative interaction being illustrated. most clearly in FIG. 8. This hook 43 is also an arcing horn. The are runs to the tip. Pivotally mounted on the free or outer end of the drag arm 39 is a nonarcing duty auxiliary contact 44 for engaging the contact 32. This is shown most clearly in FIG. 1. The contact 44 is pivotally mounted on a pin 45 and is biased against a stop 46 by means of a spring 47 about the pin 45. Attached to the rear side of the contact 44 is a piece of insulating material 48, the function of which will be described hereinafter.

As shown most clearly in FIG. 6, the arcing chamber 49 in the loadbreak device is formed between two plates 50 of insulating material, preferably material which evolves an arc extinguishing gas when an electric arc contacts the surface thereof. Examples of suitable materials are methyl methacrylate, acetal and polyamide plastics and ethyl cellulose. As shown in FIG. 6, the arcing chamber is relatively narrow so as to confine an arc drawn between the contacts and facilitate its extinction. For obtaining proper arc interrupting characteristics, the chamber 49 is not only vented by openings 51 in its radial sides, but also by openings 52 in its fiat front and back sides, these openings 52 being near the common center 36.

As shown most clearly in FIG. 9, the fixed arcing duty contact assembly comprises a fiat conductive member 53 spaced from a fiat conducting member 54 by a spacer block 55 and held together by bolts 56 passing through the loadbreak device. Integrally extending from the com ducting member 54 is a conductive strap 57 connected to the mounting bracket 29. As shown in FIG. 9, the movable contact 42 slides between the conducting

members

53 and 54 so as to make firm electrical contact therewith when the loadbreak device is in closed circuit position, in which position it is illustrated in FIG. 3.

FIG. 8 shows the loadbreak device with its contacts about half way separated and with an arc drawn between its contacts and with the arc extinguishing gases venting through the

vents

51 and 52.

The loadbreak operation of the illustrated embodiment of the invention is shown in sequence in FIGS. 10, l1 and 12. The operation is such that almost immediately after the latch has been released and the main contacts 19 and 20 separate the

auxiliary contacts

32 and 44 engage each other so that any are which starts to form between the main contacts 19 and 20 will immediately be short-circuited through the engaged

contacts

32 and 44 in series with the closed arcing duty contacts 42 and 5354 of the loadbreak device 2.

FIG. 10 shows the parts in the positions they occupy when the casting 16 is emerging from between the guide cars 17 in which position the main contacts 19 and 20 are well separated and the auxiliary contact 32 has pivoted about its axis a very substantial angle away from the stop 31. The arcing duty contacts of the loadbreak device 2 are still closed as indicated by the drag arm 39 being tight up against the side of the load-break device. This action continues as the arm 8 continues to turn in a clockwise direction, the contact 32 also turning in a clockwise direction about its pivot support until it reaches the angular position shown in FIG. 11 where contact 32 will be substantially tangent to a circle whose center is at the trunnions 14. During this clockwise angular movement of the arm 8 the movable arcing duty contact 42 is also withdrawn from the stationary arcing contact assembly 38 in the loadbreak device 2 thus drawing an arc in its arcing chamber which due to its elongation and the combined snnfiing action of the restricted volume of the arcing chamber and the arc evolved gases produced will cause extinction of the arc and interruption of load current when or before the arcing duty contacts reach their extreme separation distance shown in FIG. 11. Continued clockwise angular rotation of the arm 8 will next cause the

contacts

44 and 32 to pull apart as indicated by the positions of the parts shown in dashed lines in FIG. 12. Immediately thereafter, the loadbreak device 2 will snap shut through the action of its spring 41 so that the loadbreak device 2 automatically returns to its normally closed position, the parts then being in the positions shown in full lines in FIG. 12 which also shows that the contact 32 has snapped back to its normal position against the stop 31 by the action of its spring 33.

The operation of the device on a closing stroke is shown in sequence in FIGS. '13 and 14. In FIG. 13 as the arm 8 returns through counterclockwise rotation about its trunnions 14 to a position'in which the casting 16 is between the guide ears 17 and the main contacts 19 and are approaching their latched closed position, the insulating member 48 on the back of the pivoted contact tip 44 on the end of the drag arm 39 will pivot clockwise but no current flows through the loadbreak device because of the nonconductivity of the part 48. When .the arm 8 is slammed home and latched so that the circuit is re established through the main contacts 19 and 20 the pivoted tip 44-48 on the arm 39 clears the contact 32 and snaps from the dashed line position shown in FIG. 14 to its normal position shown in solid lines in which it is against its stop 46 and is essentially in line with the arm 39. The parts are now returned to their original position shown in FIG. 1. In this manner, the circuit is always first reestablished through the fuse in the fuse tube 9 so that in case there should be a short circuit or other abnormally high current due to a fault in the external circuit the fuse Will be able to interrupt that current. Furthermore, this high current will not pass through the contacts in FIG. 9 and weld them permanently closed.

While there have been shown and described particular embodiments of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention, and therefore it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. The combination with an open type cutout having a conducting arm hingedly supported at one end and a movable main contact at the other end for latched closed engagement with a fixed main contact, of an enclosed loadbreak device fixedly mounted on said conducting arm, said loadbreak device having an external pivotally attached drag arm and a pair of internal arcing duty contacts spring biased closed, one of said arcing duty contacts being connected to said movable main contact and the other being connected to said drag arm, a contact tip on said drag arm having an insulating rear face, and a yieldable contact in the path of movement of said contact tip connected to said fixed main contact.

2. The combination with an open type cutout having a conducting arm hingedly supported at one end and a movable main contact at the other end for latched closed engagement with a fixed main contact, of a loadbreak device fixedly mounted on said conducting arm, said loadbreak device having a pair of normally closed internal contacts and an external drag arm with a pivoted tip external contact having an insulating rear face, a pivoted external contact in the path of movement of said pivoted tip external contact and electrically connected to said fixed main contact, one of the internal main contacts of said loadbreak device being connected to said movable main contact, the other internal contact of said loadbreak device being connected to said contact tip on said drag arm.

3. The combination with an open type cutout having a conducting arm hingedly supported at one end and a movable main contact at the other end for latched closed engagement with a fixed main contact, of a loadbreak device fixedly mounted on said conducting arm, said loadbreak device having a fixed arcing duty contact electrically connected to said movable main contact, a drag arm on said loadbreak device carrying a movable arcing duty contact normally engageable with said fixed arcing duty contact, a spring for biasing said drag arm against a side of said loadbreak device for closing said arcing duty contacts, a pivotally mounted contact tip on the free end of said drag arm, a spring for biasing said tip against a stop on said drag arm which limits the angular movement of said tip relative to said drag arm in an angular direction opposite the angular direction in which the drag arm is spring biased toward the loadbreak device while permitting said tip to pivot on the drag arm in the opposite direction, an insulating rear face on said contact tip, and a contract in the path of movement of said contact 6 tip carried by a pivotally mounted arm electrically and mechanically connected .to said fixed main contact, .said last mentioned arm being spring biased against a stop .for limiting its angular motion in a direction opposite to the angularmotion of said hingedly supported conducting arm when said .main :contacts are moved apart said stop .beingmounted on said cutout.

4. The combination with an .opentype fuse cutout having an insulating .fuse tube hingedly supported at one end and provided with a switch stick eye carrying a movable main contact at the other end for latched closed engagement with a fixed main contact, a loadbreak accessory comprising a hollow vented arcing chamber formed of arc extinguishing gas evolving solid insulating material in the shape of a sector of a circle, a fixed arcing duty auxiliary contact in said chamber at one end of the portion thereof forming a segment of said circle, means for electrically connecting said movable main contact and said fixed arcing duty auxiliary contact, said means also mechanically supporting said loadbreak accessory from said movable main contact, an external drag arm pivotally attached to said chamber on a perpendicular axis passing through the center of said circle and spring biased against a side of said chamber, an elongated movable arcing duty auxiliary contact attached to said drag arm and extending into said chamber, said elongated movable arcing duty auxiliary contact being curved to conform to said segment of said circle and having its free end engageable by said fixed arcing duty auxiliary contact, said free end having a laterally extending arcing tip portion for engaging a wall of said chamber to prevent its withdrawal from said chamber, and a pair of normally separated cooperating non-arcing duty auxiliary contacts pivotally mounted respectively on the free end of said drag arm and on the support for said fixed main contact, the nonarcing duty auxiliary contact which is pivotally mounted on the drag arm being electrically connected to said elongated movable arcing duty auxiliary contact and being spring biased against a stop for limiting its angular motion about its pivot in a direction corresponding to the angular direction of said fuse tube about its hinge support when said main contacts are being closed, said last mentioned non-arcing duty auxiliary contact having a rear face of insulating material, the other non-arcing duty auxiliary contact being spring biased against a stop which limits its angular motion in the same direction that the pivotal motion of the drag arm supported auxiliary contact is limited, whereby when said main contacts are unlatched and swung open by a firm pull on a switch stick whose hook engages said eye while load current is flowing between said main contacts an arc will momentarily be drawn between said main contacts until the front conducting face of said drag arm supported non-arcing duty auxiliary contact engages its cooperating non-arcing duty auxiliary contact whereupon the are between the main contacts is short-circuited through the two pairs of auxiliary contacts and through the said loadbreak accessory and is thus extinguished, continued opening movement of said main contacts causing pivotal motion of the non-arcing duty auxiliary contact which is mounted on the support for the fixed main contact until it attains a position substantially perpendicular to said drag arm, whereupon the drag arm pivots about its support and causes progressive separation of the arcing duty auxiliary contacts in the arcing chamber thus breaking the load current, continued opening movement of main contacts causing the arcing tip on the free end of the segmental arcing duty auxi'iary contact to engage the wall of the arcing chamber and prevent further separation of the arcing duty auxiliary contacts and hence further pivotal motion of the drag arm relative to the arcing chamber, continued separation of the main contacts causing the non-arcing duty auxiliary contacts to separate thus permitting the drag arm biasing spring to snap the loadbreaks auxiliary arcing duty contacts closed, and whereby on reversing the operation of 7 8 the switch stick and causing a closing motion of the main References Cited contacts the insulating rear face of the drag arm sup- UNITED STATES PATENTS ported non-arcing duty contact engages the other nonarcing duty auxiliary contact thus causing the drag arm mounted non-arcing duty contact to pivot against the 5 torque of its biasing spring and slip past the other nonarcing duty auxiliary contact thus permitting reclosing BERNARD GILHEANY P nmary Exammer' of the main contacts without allowing current to flow GEORGE HARRIS, Examiner.

through the loadbreak accessory and with the parts of the LEWITTER Assistant Exam-Mn loadbreak accessory restored to their original positions;

3,235,688 2/1966 Fink et a1. 200114 3,145,283 8/1964 Date et a1. 200149