US2308026A

US2308026A - Load break disconnect

Info

Publication number: US2308026A
Application number: US319897A
Authority: US
Inventors: Herbert L Rawlins
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1940-02-20
Filing date: 1940-02-20
Publication date: 1943-01-12
Anticipated expiration: 1960-01-12

Description

' INVENTOR Herb erll. H aw I ins 2 Sheets-Sheet l H. L. RAWLINS LOAD BREAK DISCONNECT ,Filed Feb. 20.

Jan. 12, 1943.

WITNESSES:

ATTO Patented Jan. 12, 1943 LOAD BREAK DISCONNECT Herbert L Rawlins, Wilkinsburg, Pa., assignor a.

Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 20, 1940, Serial No. 319,897

6 Claims. (Cl. 200-62) My invention relates generally to electric circuit interrupting devices, and more particularly to disconnecting switches which are capable of interrupting load currents.

Disconnecting switches of the ype where a conducting blade member is mounted for movement into and out of engagement with respect to one 1 separated from a cooperating contact.

Another object of my invention is to provide a disconnecting switch having a mainblade, with novel auxiliary interrupting blade means operable to quickly interrupt the circuit after the main disconnecting switch blade has moved to an open position.

A further object of my invention is to provide a disconnecting switch of the type described having quick acting auxiliary blade means, with novel are extinguishing means for the auxiliary blade.

A further object of my invention is to provide as an attachment for a standard type of disconnecting switch blade, a novel auxiliary blade unit of the quick-break type.

Another object of my invention is to provide a novel arc chute structure adapted to cooperate with separable contacts of a circuit interrupter to suppress and extinguish the arc formed upon separation of such contacts.

Another object of my invention is to provide a novel are chute structure which is designed as an attachment for a standard type of disconnecting switch structure.

These and other objects of my invention will become more apparent upon consideration of the following specification of a preferred embodiment thereof, taken in connection with the attached drawings, in which:

Figure 1 is a side elevatlonal view of a disconnecting switch embodying my invention;

Fig. 2 is a view similar to'Fig. 1 showing the disconnecting switch in a partially open position, and having a portion' of one wall of the arc chute broken away to illustrate the interior construction thereof; I

Fig. 3 is a partial transverse, cross-sectional view through the arc chute substantially on the line III-J11 of Fig. 1 and illustrating the main disconnecting switch in elevation;

Fig. 4 is a transverse, cross-sectional view taken through the arc chute substantially on the line IVIV of Fig. l and showing the main disconnecting switch blade and contact in elevation;

Fig. 5 is a cross-sectional view of the auxiliary blade supporting means taken substantially on the line VV of Fig.3 and showing a portion of the main switch blade; and

Fig. 6 is a view similar to Fig. 5 with the parts in a position corresponding to that shown in Fig. 2.

Referring to the drawings and particularly to Figs. 1 and 2 thereof, I have shown portions of spaced supporting insulators 2 and 4, respectively, for supporting a disconnecting switch embodying the novel features of my invention. As shown, the supporting insulator 2 has secured to the end cap 6 thereof as by the machine screws 9, a contact base member 1 having an integral depending terminal portion 8 for the connection of a line conductor thereto. The contact support I may be of any suitable conducting material such, for example, as copper or the like, and further includes an outstanding integral hinge tongue H) for pivotally supporting the disconnecting switch blade [2. As appears more clearly from Figs. 3 and 4, the switch blade I2 is of a split construction, and includes the spaced blade sides I4. The blade sides I are pivotally mounted on the hinge tongue III with the sides located on opposite sides of the hinge tongue, respectively, by a hinge bolt I6 passing through the blade sides and hinge tongue, with resilient, cup-shaped spring washers l8 disposed between the head of the bolt andits nut, and the outer sides of the blade sides H. The hinge mounting for the blade thus far described is of a conventional type and may include limited area contact portions forming the contact between the blade sides 14 and the hinge tongue III in substantially the same manner disclosed in the copending application of H. J. Crabbs, Serial No. 268,906, filed April 20, 1939, and assigned to the same assignee of this application.

The insulator I, at the break end of the disconnecting switch blade is also provided with end cap 20, on which is seated an auxiliary blade contact supportingbase member 22, which in turn is clamped or secured to the insulator 4 together with the break contact base member 24, by the bolts 28 passing through these members to find threaded engagement in the insulator cap 2!. The break contact base member 24 is provided with an integral upstanding break tongue 28, which is slotted at its outer end as shown at 30 (Fig. 3) to receive a bolt 32 connecting the break ends of the blade sides M. The bolt 32 extends through the blade sides l4, and resilient cupshaped washers 34 at the outer sides thereof, to maintain the blade sides together. A spacing sleeve 33 is provided on the bolt 32 between the blade sides l4 for preventing undue movement of the blade sides towards each other. An operating handle 36 is secured between the outer ends of the blade sides l4 in any desired manner, such,

' for example, as by rivets or the like, and includes an aperture 31, for the reception of a hookstick operating member or the like. The break end of the blade may also be provided with raised limited area contact portions 38 for engaging the break tongue, and such contact portions may be of the type disclosed in the above-mentioned copending application.

The structure thus far described is in many respects conventional disconnecting switch structure, which may be operated to interrupt the circuit merely by pivoting the switch blade l2 in a counter-clockwise direction about its pivot l6, as viewed in Figs. 1 and 2. Such switch structures, however, are generally incapable of safely interrupting load currents, inasmuch as they depend entirely upon attenuation of the are formed when the switch blade is opened, to increase the arc voltage and extinguish the arc. Obviously, especially in high voltage applications, the arc may not be extinguished until the switch blade has been opened a substantial distance and the arc formed being exposed, may jump to adjacent apparatus or even to the operator. Therefore, I have incorporated as a part of .a conventional disconnecting switch structure, to render such switches capable of interrupting load currents even at high voltages, and to extinguish any arcs formed upon opening the switch in a relatively minor portion of the opening movement of the switch, with such arcs entirely confined, to thereby eliminate all danger in the operation of the switch, and provide a' switch which is capable of interrupting load currents in a relatively simple, yet efiicient, manner. The interrupting structure which I have devised furthermore is capable of attachment to conventional types of disconnecting switches in a relatively simple man gswitch blade l2, and extends outwardly through the open space in the. U-form side wall of the block 42, with the head thereof positioned at a point spaced inwardly of the opposite wall 46 of the block 42. A spacer sleeve 56 is provided on the bolt 54 between the head thereof and the adjacent blade side M to position the head of this bolt, as shown in Fig. 3. A second spacing sleeve 58 is provided on the bolt 54 between the blade I sides l4, to maintain the same in spaced relation. The bolt 54 is provided with a nut 60 to secure the same in position.

As stated above, the wall 48 of the auxiliary blade supporting block 42 is substantially U- shaped in form, as shown in Figs. 5 and 6, to provide a pair of spaced substantially radially extending

stopshoulders

62 and 64, respectively, with the stop bolt 54 having the end thereof received in the space between the stop shoulders 62 ner and without involving any extensive modifl- V cation of such existing switches.v

I provide an auxiliary switch blade 40 which, as appears from Figs. 1 and 2 of the drawings, has its outer end tapered, with the inner end thereof substantially rectangular in form and secured to a supporting block 42 which is in turn pivotally mounted on the main disconnecting switch blade l2. The auxiliary blade 40 is secured to the supporting block 42 as, for example, by the machine screws 44. The supporting block 42 is in the form of a casting, or the like, having one side wall 46 to which the auxiliary blade 46 is secured, and an opposite side 48 which is generally U- shaped in form, and which is seated upon the outer side of the blade side l4. The main disconnecting switch blade I2 is modified solely by the provision of a pair of laterally spaced apertures extending through both blade sides l4, for mounting the auxiliary blade 40 thereon. A pivot bolt 50 extends through the auxiliary blade 40, the auxiliary. blade supporting block 42,-and

through one of the apertures through the main blade l2 to pivotally support the block 42. The pivot bolt 50 is provided with a

spacer sleeve

52 and 64. A coil spring 66 is provided about the spacing sleeve 52 and has one end thereof engaged with an inner extension of one screw 44,

as is clearly shown in Figs. 3, 5 and 6., The otherend thereof is extended to engage the stop bolt spacer sleeve 56, which is fixed to the main disconnecting switch blade l2 by bolt 54. As is apparent from Figs. 5 and 6, the coil spring 66 tends to maintain the supporting block 42, and consequently the auxiliary switch blade 40, in the position in which it is substantially parallel to the main disconnecting switch blade I2 and wherein the stop shoulder 64 of the switch block 42 is maintained in engagement with the stop bolt 54. This is the normal position of the auxiliary switch blade 40 with respect to the main switch blade l2 and is illustrated in Figs. 1, 3, 4 and 5.

Referring to Fig. 4, it will be observed that the supporting base member 22 is provided with an integral substantially perpendicularly disposed projecting flange portion 12 for supporting a contact cooperative with the auxiliary blade, and an arc chute structure. Contact strips I4 are disposed at opposite sides of the flange l2, backed by resilient leaf contact springs 16, with insulating plates 18 enclosing the contact structure, and

all beingsecured to the flange 12 by the bolts 80, extending through the contact strips 14, spring members 16, insulating plates 18, and the supporting member 12., The supporting flange 12- a slot for the'reception of the outer end of the auxiliary switch blade 40 therebetween. The contact strips 14 are clamped in position, as shown in Fig. 4 so that the outer ends thereof converge slightly, and the inner sides of the outer edges are turned inwardly and then outwardly, to form inwardly convex, opposed surfaces on the outer edges of the contact strips 74. The contact strips 14, supporting flange l2 and base 22 may be of any desired conducting material such, for example, as copper or the like. The contact strips 14 are resiliently backed and maintained against separation by the leaf spring members 16 intimately engaged with the outer sides of these contact strips. The leaf spring members 16 may be of any desired resilient material such, for example, as phosphor-bronze or the like. The insulating plates 18 may be of any desired insulating material such, for example, as a moulded insulating material, fiber, or. the like and have the outer edges thereof beveled,,as shown in Fig. 4 to provide a converging entrance to the slot between these plates. The plates 18 are preferably provided with liner plates 83 which have cut-out portions or slots 82, as shown in Fig. 2 for receiving the contactstrips l4 and their resilient backing members 16. The liner plates 83 are preferably of a material which is capable of evolving an arc extinguishing gas when in proximity to an electric are such, for example,

' as fiber, boric acid, or a synthetic resin. The

liner plates are secured in position with respect to the insulating plates 18 as by the screws 8| If desired, the insulating plates 18 may be of a gas evolving material similar to plates 80, in which event the liner plates may be dispensed with.

Whether or not the insulating plates 18 are provided with liner plates 83, the slot provided between the plates for the reception of the auxiliary blade 40 should be substantially equal to the thickness of the blade, and in any event, should be less than twice the blade thickness to obtain effective arc extinguishing properties. The auxiliary blade Ill itself is preferably very thin so that the slot formed between the insulating members 18 may likewise be thin. Thus, for example, in one form of switch constructed in accordance with this invention and which was built and successfully tested, the slot was about /8" wide and the switch successfully interrupted currents of 400 amperes at 2300 volts, and 200 amperes at 4600 volts.

As shown in Figs. 1, 3, 4 and 5, the switch is in its normal closed position with the main switch blade 12 in engagement with its break contact tongue 28, and with the auxiliary switch blade 80 received between the contact strips H in the arc chute. When it is desired to interrupt the circuit, the operating member 31 on the main switch blade I2 is moved in a direction to move the main blade l2 in a counter-clockwise direction from that shown in Fig, 1 to that shown in Fig. 2. This will separate the main switch blade 12 from contact tongue 28 and cause slight movement of the outer end of the auxiliary blade 30 from the position shown in Fig. 1 to a position where it engages the inwardly turned outer ends of the contact strips H, as shown in Fig. 2. The outer end of the auxiliary blade is'retained in this po. sition for a substantial amount of the opening movement ofthe main switch blade by the inwardly turned ends of the contact strips 14, so that even through the main switch blade is in an open position the circuit is still unbroken through the switch, since it is shunted through the auxiliary blade 48 and contact strips 14. In the movement of the main switch blade from the position shown in Fig. 1 to the position shown in Fig. 2, the auxiliary blade 48 will move relatively clockwise about its pivot. with respect to the main switch blade l2. This relative movement between the main switch blade and the auxiliary switch blade 48 will act to stress the coil spring 66 mounted in the block 42, and these parts will assume the position shown in Fig. 6. When the parts arrive at the position shown in Figs. 2 and 6, the shoulder 62 on the supporting block 42 comes into engagement with the stop bolt 84 which is fixed relative to the main switch blade l2. Relative movement between the two blades is thereby prevented upon continued movement of the main switching blade l2 in the opening direction, and upon such continuation of movement, the auxiliary blade All is pulled clear of the inwardly turned outer ends of the contact strips 14, thereby permitting the coil spring 66 to quickly move the auxiliary blade 40 with a snap action out through the slot in the arc chute to a position in which it is again substantially in parallel relation with respect to the main switch blade i2. This movement of the auxiliary blade 48 through the arc chute will extinguish the are formed in a manner to be hereinafter referred to while confining it within the arc chute. The switch may thereafter with safety, be moved to a full open position. To close the switch, the main blade I2 is moved in a clockwise direction from its open position and both the main blade l2 and the auxiliary blade 40 are brought into engagement with their respective contacts 28 and H, substantially simultaneously to close the circuit. In the closing operation the blades are constrained to move together since engagement of shoulder 64 of block 42 with stop bolt 54, prevents relative counter-clockwise movement of the auxiliary blade. In the closing operation, when the auxiliary blade 40 engages the outer ends of contact strips 14, it is enabled to supply force to provide an entrance therebetween by its engagement with the outer inwardly convex portions of the contact strips 14. Separation of the contact strips 14 is permitted by yielding of the resilient backing strips 16 in engagement therewith. As appears in Fig. 4, normally the free.end of the auxiliary switch blade 40 lies below the outer inturned ends of the contact strips H, and may be entirely out of engagement with respect to the strips. The only time that it is necessary for the auxiliary blade 40 to engage the contact strips 14 is during the opening movement of the switch to shunt the circuit therethrough, as heretofore described.

As stated heretofore, the slot provided between the insulating members 18 and may be extremely narrow due to the use of a very thin auxiliary blade 40, and this allows the provision of a small clearance between the blade and the insulating

members

18 and 83. Therefore, when the auxiliary blade is snapped open, the arc is not only attenuated to increase its arc voltage as in conventional switch structures, but is also conlined in a narrow slot which additionally acts to increase the arc voltage, and furthermore, when a lining 83 of gas evolving material is used, the arc flowing between the spaced walls of such material is subjected to such evolved un-ionized gases to thereby extinguish the are at a current zero and prevent restriking of the same. With the structure which I have disclosed, therefore, it -is apparent that there are three factors which contribute to extinguishing the are formed upon opening the switch, namely: (1) lengthening of the arc, (2) confining the arc in a narrow space, and (3) subjecting the arc to a blast of un-ionized gas. It is apparent that the supporting fiange member 12 acts to close the bottom of the slot between

arc chute plates

18 and 83, as viewed in Fig. 4, and the outer adjacent side of the slot is closed by an insulating spacer member 19, as

shown in Fig. 3, whereby the gas evolved from the lining material '83 is forced to pass out of the slot in the arc chute at the two remaining sides of the slot. This will act to increase the effect of the gas blast produced by the gases evolved by the lining 83 when subjected to an electric arc. It should be noted that the depth of the slot is many times thewidth of the portion of the auxiliary blade 40 received therein, and is proportioned substantially so that when the auxiliary blade fsnaps open, the main switch blade I2 is still in a position substantially in the plane of the arc chute so that the auxiliary blade 4!! acts to interrupt the circuit substantially entirely within the arc chute slot so as to confine the are formed to the chute. In other words, the break distance of the auxiliary blade is substantially entirely confined to the slot in the arc chute.

From the foregoing it should be apparent that I have provided a novel disconnecting switch structure capable of interrupting load currents with safety and with less travel of the discon necting switch blade than has heretofore been possible. Also, I have provided a quick opening auinliary blade structure especially constructedand adapted for ready attachment to conventional switch blade structures at one side of such blades, it being necessary merely to provide two apertures through the blade to attach my novel auxiliary blade structure thereto. I have also provided a novel are extinguishing structure for use with the auxiliary blade structure described above, and which also can be readily attached to a disconnecting switch contact structure.

As stated heretofore, the entire arc chute structure, together with the break contact for the auxiliary blade, is supported by a single support member 22 which can be secured to the maiii disconnecting switch break contact and its insulator support, utilizing the bolts which normally support the main break contact on the insulator. Also, it should be noted that in the closed position of my novel switch structure, the auxiliary blade contacts are contained within an arc chute structure together with the outer end of the auxiliary blade, and the are formed is substantially entirely confined within this structure and is entirely extinguished upon relatively slight movement of the auxiliary switch blade away from its opposed contacts 14.

Although I have shown my novel interrupting structure as applied to a conventional disconnecting switch wherein this structure has certain particular novel features of cooperation, it should be obvious that the auxiliary blade structure, together with the arc chute structure therefor, is also capable of use with other types of blades, finding particular utility, for example, in an enclosed type of disconnecting switch wherein the opening movement is determined by the size of the switch enclosure. Therefore, it is obvious that an enclosed switch constructed in accordance with my invention will be capable of interrupting load currents in a smaller enclosure than the conventional type of disconnecting switch because of the relatively small travel of the blade structurenecessary to open the circuit and extinguish the arc formed. Similarly, my invention may also be applied to other types of circuit interrupters where it is desired to utilize a disconnecting function by providing an air gap in the circuit, such, for example, as in a disconnecting type of fuse.

Having described a preferred embodiment of my invention in accordance with the patent statutes, I desire that it be understood that my invention is not to be limited to the particular embodiment disclosed, inasmuch as it will be obvious, particularly to persons skilled in the 'art,

that many changes and modifications may be made in the embodiment disclosed without departing from the broad spirit and scope of the invention. Therefore, I desire that my invention be interpreted as broadly as possible, and be limited only by what is expressly set forth in the following claims.

I claim as my invention: I

1. As a new article of manufacture, an attachment for switch blades including an elongated auxiliary blade member having secured adjacent one end, thereof a mounting and spacing block projecting from one side of said member, a pivot aperture through said blade and block assembly for the pivotal mounting of said attachment, and spaced laterally extending shoulders on said block adapted to providestop means for limiting piv-' otal movement of said blade member.

2. As a new article of manufacture, an attachment for switch blades including an elongated auxiliary blade member having secured adjacent one end thereof a mounting and spacing block projecting from one side of said member, a pivot aperture through said blade and block assembly for the pivotal mounting of said attachment, and opposed shoulders on the side of said block opposite said blade member spaced from the axis of said pivot aperture and relatively angularly displaced about said axis to provide stop means for limiting pivotal movement of said blade member.

3. In a switch, contact means, main blade means mounted for movement into and out of engagement with said contact means, auxiliary quick-break blade means comprising an elongated auxiliary blade member having secured adjacent one end thereof a mounting and spacing block projecting from one side of said member, a pivot aperture through said blade and block assembly for the pivotal mounting of said auxiliary blade means, opposed shoulders on vthe side of said block opposite said auxiliary blade means spaced from the axis of said pivot aperture and relatively angularly displaced about said axis, a pivot pin passing through said pivot aperture and an aperture in said main blade means to pivotally meat s at a position relativeto said main blade means such that it is positively moved with said main blade means into engagement with said contact means, and said resilient means causes movement of said auxiliary blade means with said main blade means in a direction out of engagement with said contact means.

4. An attachment for the break contact of disconnecting switches comprising an arc chute unit, said unit including spaced, substantially parallel walls of insulating material defining a narrow slot therebetween, supporting means of conducting material secured between said walls adjacent one edge thereof, contact means in said slot secured to said supporting means, said supporting means extending outwardly of said walls and having a laterally extending supporting portion of such size and shape as to'be secured between the break contact and its supporting insulator of a disconnecting switch, so as to support contact with said contact means electrically connected therewith and arranged so that said'slot is located so as to receive an auxiliary snap-acting blade operatively associated with the blade of said switch.

5. An attachment for the break contact of disconnecting switches comprising an arc chute unit, said unit including spaced, substantially parallel walls of insulating material defining a narrow slot therebetween, supporting means of conducting material secured between said walls adjacent one edge thereof, contact means in said slot secured to said supporting means, said supporting means extending outwardly of said walls and having a laterally extending flat supporting portion adapted to be secured between the break contact and its supporting insulator or a disconnecting switch, so as to support said unit from the same insulator supporting said break contact in a position adjacent said break contact with said contact means electrically connected therewith and arranged so'that said slot is located so as to receive an auxiliary snap-acting blade operatively associated with the blade of said switch.

' as to be secured between the break contact and 6. An attachment for the break contact of disconnecting switches comprising an arc chute unit, said unit including spaced, substantially parallel walls oi insulating material'deilning a narrow slot therebetween, means including supporting means of conducting material secured between said walls adjacent one edge thereof for maintaining said walls in predetermined spaced relation and closing said one edge of said slot, contact means in said slot secured to said supporting means, said supporting means extending outwardly of said walls and having a laterally extending supporting portion of such size and shape HERBERT L. RAWLINS.