US2834855A

US2834855A - Load break device

Info

Publication number: US2834855A
Application number: US578995A
Authority: US
Inventors: Thomas J Carpenter; Jr Sidney R Smith
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1956-04-18
Filing date: 1956-04-18
Publication date: 1958-05-13
Anticipated expiration: 1975-05-13

Description

May 13, 1958 T. J. CARPENTER ET AL 2,834,855

LOAD BREAK DEVICE Filed Aug. 1e, 195e pmlmmllll 27 United States Patent LOAD BREAK DEVICE Thomas J. Carpenter, Pittslield, and Sidney R. Smith, Jr., Stockbridge, Mass., assignors to General Electric Cornl pany, a corporation of New York Application April 18, 1956, Serial No. 578,995

Claims. (Cl. Zim- 143) This invention relates to a load break device, and more particularly, to a load break device useful in electric switches such as manually operable knife switches and automatically and manually operable circuit interrupters such as open and enclosed type cutouts.

In the conventional cutout a fuse link is provided to automatically disconnect or sectionalize the protected apparatus or electrical circuit from the remainder of the line in case of heavy overloads or short circuits in the apparatus or circuit. Sometimes, as when it is desired to make repairs on the protected apparatus the same is disconnected by manually opening the cutout. When the load current is broken in this manner it is not unusual for a heavy electrical arc to be drawn between the separated contacts. The higher the circuit voltage and load current the more pronounced the arcing is apt to be, and the more difficult to interrupt in this manner. Such arcing may be dangerous to the safety of the lineman even though he opens the switch with a switch stick. For example, a heavy wind may -fblow the arc about and cause it to strike the lineman or a grounded object in which event a major short circuit to ground is established. Also, arcing has a detrimental effect on the cutout structure causing pitting and erosion of the contacts and initiating corrosion of other parts. Of course, if the arc persists it may be extinguished by reclosing the cutout. However, if an arc has 'been drawn the chances are that the protected apparatus is operating at relatively high currents and similar arcs will be drawn upon subsequent openings of the cutout. Therefore, it is very desirable to provide a load break device in a cutout or switch to automatically extinguish the electrical arc accompanying manual opening of the cutout or switch.

Load break devices in cutouts or switches are not new per se. However, many of the prior art load break devices tend to be rather complicated and costly. ln fact, some of the prior art load break devices appear to be almost as complicated and costly as the cutout itself. inasmuch as occasion for manually breaking the load arises rather infrequently it will be appreciated that it is very desirable to provide a load break device which is very uncomplicated and low in cost.

ln perhaps the majority of applications the users prefer the enclosed type of cutout having the fuse parts enclosed in an insulating housing. The housing is provided with a door or cover of insulating material so that the housing taken as a whole provides a measure of safety to the linemen against coming in direct contact with live parts. Although it would be possible to provide the cutout with an externally mounted load breaking means, it is particularly desirable that the load break means be in corporated inside the cutout enclosure in such a manner that there are no exposed live parts. rthis important restriction requires that the load break device be relatively small in dimensions, otherwise it would `be necessary to increase the overall cutout size to accommodate it, resulting in appreciable cost increase of the cutout.

Some of the prior art load break devices incorporate 2,834,855 Patented May 13, 1958 arc interrupting mechanisms which tend to deteriorate with use so that their effectiveness is reduced after a number of operations. Also, some of these employ complicated mechanical levers and mechanisms which are subject to friction, corrosion, and the like which reduces theirreliability after long periods of exposure to the elements. Although load breaks tend to be called upon to operate rather infrequently, it is important that their operating eiliciency not be impaired in either of the above respects.

Accordingly, it is an object of this invention to provide an uncomplicated and low cost load break device for extinguishing the electrical arc accompanying manual opening of a switch.

Another object of the invention is to provide a load break device which is physically small so it can be incorporated economically within the housing of a conventional fuse cutout so as to eliminate exposed live parts.

Another object of the invention is to provide a load break device for a switch or cutout which will not deteriorate in load interrupting ability with use.

Another object of the invention is to provide a load break device for a switch or cutout which has a minimum of moving parts subject to inoperativeness due to friction or corrosion.

in the invention the load `break device comprises a small replaceable capsule of high pressure blast generating material to extinguish the electrical arc accompanying manual opening of a switch.

While the speciiication concludes with claims particularly pointing out and distinctly claiming the subject mattei' which we regard as our invention, it isbelieved the invention will be better understood from the following description taken in connection with the accompanying drawing in which:

Fig. l is a partly broken away side elevation view of a conventional form of enclosed type fused cutout embodying one form of our invention; and

Fig. 2 is a view similar to that of Fig. l except that the fuse tube assembly is in a partial open position; and

Fig. 3 is also a view similar to that of Fig. l except that the fuse tube assembly has been moved to a still further open position; and

Fig. 4 is a view similar to that of Fig. 3 except that the parts have been illustrated on a larger scale and in greater detail; and

Fig. 5 is a view of the parts of Fig. 4 when viewed from the right side of Fig. 4; and

Fig. 6 is a partly broken away side elevation view of another form of our invention; and

Fig. 7 is a bottom view of the structure illustrated in Fig. 6.

Referring now particularly to Figs. l and 2, illustrated therein is an enclosed type fused cutout comprising a porcelain or other electrical insulating material housing l having .a pair of spaced terminal contacts Zand 3 mounted therein. The

lterminal contacts

2 and 3 have terminal clamps 4 and 5 respectively electrically associa-ted therewith. The terminal clamps are adapted to receive the insulation stripped ends 6 and 7 of a pair of line leads. The ends 6 and 7 can be inserted into the housing 1 through a pair of not shown apertures formed in the sides of housing 1 adjacent to the terminal clamps 4 and Also, the cutout may be mounted `on the crossarm of a line pole by virtue of a strap 8 cemented or otherwise fastened into the back of housing 1.

An electric circuit is completed through the

terminal contacts

2 and 3 by a fuse tube assembly comprising a fuse tube or holder 9 and a fuse link 10 disposed therein. The Ifuse tube assembly is carried by an electrical insulatments and 16 mounted on the door 12 and in housing 1 respectively.

The upper end of the tube 9 is closed by a cap 17 and disposed adjacent the bottom and inside of door 11 is a hinge element 18. The fuse link 1) is electrically connected at its upper end to upper fuse tube contact 13 in a manner well known to those skilled in the art, and the lower end of the fuse link 10 extends out of the open lower end of fuse tube 9 and is electrically connected to the hinge element 18 by a thumbscrew 19 or the like. The fuse tube assembly .and door 11 is hinged with respect to the housing 1 and the

terminal contacts

2 and 3 iby virtue of a pivotal connection between the hinge element 18 and a pai-r of trunnions 20 which are fixed in the lower end of housing 1. `In the particular form of cutout shown the lower fuse tube contact 14 is electrically connected to the lower end of fuse link 1i) when it is fastened to hinge element 18 inasmuch as contact 14 and hinge 18 are integral extensions of each other, although other means may be employed to electrically connect fuse link 10 to contact 14.

In the closed position of door 11 an electrical circuit is completed from line lead 6 through

parts

4, 2, 13, 10, 18, 14, 3 and 5 to line lead 7. If an overcurrent occurs the fuse link 10 will fuse to interrupt the circuit. The inside `of fuse tube 9 may be coated or lined with a gas evolving material so that when an arc is drawn within fuse tube 9 upon `fusing of element 1t) gases will be expelled out of the lower open end of tube 9 to aid in extinguishment of the arc. Only -those parts of the cutout have been described which are believed necessary for a complete understanding of the invention, and the particular form of cutout shown is of the non-dropout type. However, the fuse tube assembly and door may be arranged to automatically drop out to give a visual indication of fusing of link 10, -or other visual indicating means may tbe employed. The illustrated cutout and modifications thereof are illustrated in detail in copending patent application Serial No. 375,902, filed August 24, 1953,

now vPatent 2,744,982, dated May 8, 1956, and assigned to .the same assignee as -the instant case.

When it is desired -to manually interrupt the circuit or break the load the door 11 and the fuse tube assembly may be hinged open by hooking a switching stick in handle 12 and pulling outwardly.

In Fig. 2 an arc 21 is illustrated as being drawn between the

contacts

2 and 13 when the door 11 is opened to manually interrupt the electrical circuit. An arc would also normally be drawn between

contacts

3 and 14 were it not for certain parts of the invention to be described hereinafter. In `our invention ya small replaceable cartridge case, capsule, or receptacle of high pressure blast generating material is utilized to interrupt the electrical a-rc accompanying manual opening of the switch.

Referring now also to Figs. 3 to 5, in the iirst form of our invention the high pressure lblast generating means comprises a very small replaceable cartridge of compressed carbon dioxide gas. The various parts of the cutout and load break device are so constructed and correlated that when door 11 is opened the last point of electrical contact between-the fuse tube assembly and the

terminal contacts

2 and 3 is between the `tip of the cartridge 22 and a part of the lower terminal clamp 5 whereby `an electrical arc 23 will be drawn therebetween (see Figs. 3 and 4.) The tip of cartridge 22 is a hollow protuberance whose side walls are very lthin as compared to the remainder of the cartridge, for example, the order of `a few mils thickness. Accordingly, when the arc 23 impinges or terminates on the tip of cartridge 22 the tip will be punctured whereby the canbon dioxide gas will be released from within cartridge 22 -to put out the arc 21. When gas is released from cartridge 22 it will be directed against the rear of housing 1 and then reflected therefrom across the arc 21 to put out the same. The sudden expansion of the carbon `dioxide gas from within the cartridge 22 has -a cooling effect on the tip of cartridge 22 as well as on the terminal clamp 5 and the arc 23. Since the termini of arc 23 as well as the arc 23 are cooled the carbon dixoide gas is also effective to interrupt the electrical arc 23.

Although carbon dioxide is illustrated as the chemical composition or material which provides a blast or pressure front `against the arcs the invention -is not confined to this particular material. For instance, a cartridge 22' of explosive such as shown in Fig. 6 may be used, as well as other electrical insulating gases such as nitrogen or sulfur hexatluoride. Also, small replaceable cartridges of liquids yor materials which will evolve a blast of gas or the like when having an arc playing thereon may be used in practicing the invention. Furthermore, the blast need not necessarily be initiated by the impingement of an electrical arc on the cartridge. For instance, other electrical mechanisms or even mechanical means may be used to initiate the blast. However, the illustrated manner of initiating the blast by causing the impingement of arc 23 on the tip of cartridge 22 is thought to be very advantageous inasmuch as this method requires a minimum of parts and is very low in cost.

Also, although the cartridge 22 is shown as being located adjacent the lower end of the fuse tube assembly and the lower terminal clamp 5 it will be apparent to those skilled in the art that other positions for the cartridge 22 may be provided. For example, the cartridge 22 could be mounted adjacent` the upper fuse contact 13 to draw an arc from the upper housing mounted terminal contact 2. In such an arrangement the blast could be directed directly across the upper arc instead of being vreflected off the rear of the housing 1. However, in the former arrangement special provision would need to be made to guard against accidental tiring of the cartridge 22 when the door 11 was being closed. The illustrated position of the cartridge 22 is desirable inasmuch as upon closing movement of the door 11 closure of the

contacts

3 and 14 shunts the cartridge 22 before the circuit is completed by closure of or drawing of an arc between

contacts

2 and 13, which means that there will be no accidental firing of the cartridge 22. Additionally, although the cartridge 22 requires a minimum of space it is believed that positioning the cartridge in the upper end of the cutout might interfere with the proper functioning of the upper parts of the cutout such as the

contacts

2 and 13 and latches 15 and 16 and thereby unduly complicate the upper end of the cutout.

Another reason for placing the cartridge in the bottom of the cutout is that in the Figs. 3 and 4 open position of the cutout the hinge 18 and contact 3 are electrically isolated from each other so that arc 23 will be drawn therebetween if arc 21 is present. In some open type cutouts the hinge for the fuse tube and the lower terminal contact are not electrically isolated from each other. However, this merely means that other means may need to be employed to initiate the blast or that the position of the cartridge may need to be changed. That is, the invention is not restricted to enclosed type cutout but is useful in open type cutouts as well, and may even be used in simple switches such as knife switches. At some points of the line where the load is broken frequently it is not unusual to employ a knife switch by replacing the fuse tube and its fuse link with a disconnect blade. In such a device our invention may be employed to extinguish the arc drawn to the disconnect blade.

The hinge element 18 has a generally U-shaped contiguration with the thumbscrew 19 being located in the bridge portion of the U-shaped configuration. The cartridge 22 which is replaceable is mounted in a cartridge holder 24 which in turn is carried by a spring biased arm 25. The arm is piVotally mounted on a, pin 26 which is mounted in the hinge elen'zent 18. A spring 27 coiled about the pin 26 and bearing against the bridge portion of element 18 and against the arm 2S continuously urges the cart-ridge 22 away from the fuse tube 9 and towards the vterminal contact 5. When the door 11 is opened an arc will be drawn between contacts 2 and i3 such as illustrated by reference numeral 21. Assuming that arc 21 persists, continued opening of the door 11 will cause terminal Contact 5 and the tip of cartridge 22 to part Contact whereby electrical are v23 is established and a blast of carbon dioxide gas is released from cartridge 22. Prior to closing door 11, and assuming that cartridge 22 has been punctur'ed in order to interrupt the arcs 21 and 23, the device can be reconditioned for a subsequent load break operation merely by putting a new cartridge in the car-- fridge holder 24. When the door 1l is closed the cartridge 22 will ride up 'along the terminal contact 5 and be urged against the biasing action of spring Z7' to an upright parallel position with respect to the fuse tube 9 such as illustrated in Fig. l. When the cutout is closed should an overcurrent occur in the cutout the cartridge 22 will remain intact and will not be punctured. This is because the main current flow will be from the hinge element 13 to contact 14 and contact 3 instead of from hinge element TLS through cartridge 22 'to the terminal clamp 5. Additionally, portions of the cartridge 22 other than the tip can be made suiiiciently thick so that even if there is an appreciable current flow from hinge 18 to cartridge 22 and then to terminal clamp 5 during an overcurrent the side walls of cartridge 22 will not be punctured.

In the Figs. 6 and 7 form of the invention a cartridge 22 of gunpowder is utilized to provide a blast or pressure front across the electrical arcs. Cartridge 22 is carried by a rather sturdy cartridge holder 24' which is spring mounted on hinge element 18 by a spring 27. The spring 27 is coiled about a pin 26 and is yalso looped about the lower end of cart-ridge holder 24'V in such a manner that a portion 2S yof the spring 27 serves the function of the heretofore mentioned arm 25 of the lirst form of the invention. The upper detonating cap or end of the cartridge 22 is made very thin so that when the arc 23 impinges thereon it will be pierced or sutiiciently heated so that the gunpowder will be exploded. The cartridge 22 will be ejected from the holder 24 and a blast will be directed from within the holder 24' across the arc 23 as well as against the rear of housing l. and then reiiected therefrom across the arc drawn between the upper terminal contact and upper fuse tube contact. Prior to closing of the door the load break device is reconditioned for a subsequent load break operation by placing a new explosive cartridge in the holder 24.

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 modications 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:

l. In an automatically and manually operable circuit interruptor, said interrupter having means for automatically interrupting an overcurrent therethrough, said interrupter having other means for extinguishing an electric arc established when said interrupter is manually opened, said other means comprising a replaceable cartridge which is small with respect to said interrupter, said cartridge being adapted to produce an electric arc extinguishing pressure blast into said electric arc, and means for initiating said pressure blast only it an electric arc is established when said interrupter is manually opened.

2. In an automatically and manually operable fused switch, means for extinguishing an electric arc estab- 6 lished when said switch is manually opened, said means comprising a replaceable cartridge of explosive, said cartridge being small in comparison to said switch, and means for detonating said explosive comprising means for causing an electric arc to terminate on said cartridge only when said switch is manually opened.

3. In an automatically and manually operable fused switch, means for extinguishing an electric arc established when said switch is manually opened, said means comprising a replaceable cartridge of compressed electrical insulating gas, said cartridge being small in comparison to said switch, and means for releasing said gas into said electric arc 'comprising means for causing an electric arc to terminate on said cartridge only when said switch is manually opened.

4. ln an electric switch, said switch having means for automatically interrupting an overcurrent, other means for extinguishing an electric arc established only when said switch is manually opened, said other means comprising a replaceable cartridge of material which is small in comparison to said switch and which is adapted to direct an electrical arc extinguishing pressure blast into said electrical arc by impingement of an electrical arc on said cartridge of material.

5 In an enclosed automatically and manually operable fused cutout enclosed within a housing, means for extinguishing an electric arc established when said cutout is manually opened, said means comprising a small replaceable cartridge of material which is positioned inside of said housing and which is adapted to produce an electric arc extinguishing pressure blast into said arc oniy when an electric arc is established accompanying manual opening of said cutout, and means for initiating said pressure blast when said cutout is manually opened.

6. In an enclosed type fused cutout comprising a pair of vertically spaced terminal contacts mounted in a housing and a door for said housing having a fuse tube assembly mounted thereon which has a pair of vertically spaced contacts for engagement with said terminal contacts, a hinged connection vertically below said pairs of contacts between said housing and door whereby said door may be manually hinged open and closed, said hinged connection comprising a hinge element mounted on said door, said hinge element being electrically isolated from the lower one of said terminal contacts but electrically connected to the lower one of said fuse tube assembly contacts, a terminal clamp mounted in said housing and electrically associated with said lower terminal contact, a load break device for extinguishing an electrical arc established between the upper one of said terminal contacts and fuse tube assembly contacts when said door is manually hinged open to manually interrupt load current, said load break device comprising a small replaceable high pressure blast generating electrically conductive cartridge which is mounted on said hinge element and spring biased toward said terminal clamp for contact therewith whereby the last point of electrical contact between said door mounted structure and said housing mounted structure when said door is manually opened is between said cartridge and said terminal clamp.

7. In an enclosed type fused cutout comprising a pair of vertically spaced combined terminal clamp and contact assemblies mounted in a housing and a door for said housing having a fuse tube assembly mounted thereon, said fuse tube assembly having a pair of vertically spaced contacts for engagement with the contacts portions of said combined terminal clamp and contact assemblies, a hinged connection between the bottom of said housing and door whereby said door may be manually hinged open and closed, a load break device for extinguishing an electrical arc established between the upper one of said contact portions and the upper one of said fuse tube assembly contacts when said door is manually hinged open to manually interrupt load current, said load break device comprising a small replaceable high pressure blast generating cartridge which is carried by said door and spring biased toward the lower one of said combined terminal clamp and contact assemblies for contact therewith, said cartridge having an electrically conductive contact tip thereon which is electrically connected to the lower one of said fuse tube assembly contacts and which is the last point of electrical contact between said housing mounted assemblies and said door mounted assembly when said door is manually hinged open.

8. In an enclosed type fused cutout comprising a pair of vertically spaced combined terminal clamp and contact assemblies mounted in a housing and a door for said housing having a fuse tube assembly mounted thereon, said fuse tube assembly having a pair of vertically spaced contacts for engagement with the contact portions of said combined terminal clamp and contact assemblies, a hinged connection between the bottom of said housing and door whereby said door may be manually hinged open and closed, a load break device for extinguishing an electrical arc established between the upper one of said contact portions and the upper one of said fuse tube assembly contacts when said door is manually hinged open to manually interrupt load current, said load break device comprising a small replaceable high pressure blast generating case which is carried by said door and spring biased toward the lower one of said combined terminal clamp and contact assemblies for contact therewith, said case having an electrically conductive tip thereon which is electris cally connected to the lower one of said fuse tube assembly contacts and which is the last point of electrical contact between said housing mounted assemblies and said door mounted assembly when said door is manually opened whereby an electrical arc will be established between the lower one of said combined terminal clamp CTL 8 l and contact assemblies and said conductive tip in series with said rst mentioned electrical arc when said door is manually opened.

9. In an enclosed type fused cutout comprising a pair of spaced terminals mounted in a housing and a door clement for said housing including a fuse tube assembly, contacts for engagement between said terminals and said fuse tube assembly, a hinged connection between said housing and door element whereby said door element may be manually hinged opened and closed, a load break devi/:e for extinguishing an electrical arc established between said contacts when said door element is manually hinged open to interrupt load current, said load break device comprising a small replaceable high pressure blast generating electrically conductive cartridge which is mounted on said door element and spring biasedv toward one ot said terminals for contact therewith whereby the last point of electrical contact when said door element is manually opened is between said cartridge and said latter terminal.

l0. in an enclosed type fused cutout comprising a housing, upper and lower line terminals, a hingedly mounted tuseholder, and contacts to connect said terminals and fuseholder, a blast generating cartridge mounted on said useholder whereby when said fuseholder is manually opened the last point of electrical contact is between the lower line terminal and said cartridge.

References Cited in the le of this patent UNITED STATES PATENTS