US2956138A - Operating mechanism for an electric switch - Google Patents

Description

Oct. 11', .1960 w. N LESTER EI'AL 2,956,138

OPERATING MECHANISM FOR AN ELECTRIC SWITCH Filed Dec. 2, 195a SSheets-Sheet 1 Inventors: 48 William N. Lester, Laurence D. Shaw,

Th eh" Attorn e5.

5 w. N. LESTER :r'AL 2,956,138

OPERATING'MECHANISH FOR AN ELECTRIC SWITCH Filed Dec. 2, 1958 iSheets-Sheet 2 l'nvehcorsz" Willi'am- N. Lester, V Laui-ehce D. Shaw, by Their A'tb orngg.

Oct. 11, 1960 w. N. LESTER ETAL 2,956,133

' OPERATING MECHANISM FOR ANELECTRIC swncn Filed Dec. 2, 195a SSheets-Sheet 3 Inventors: William N. Lester, Laurence D. Shaw,

by Their Attorney;

United States Patent OPERATING MECHANISM FOR AN ELECTRIC SWITCH William N. Lester, Norwood, Pa., and Laurence D. Shaw,

Haddonfield, N.J., assignors to General Electric Company, a corporation of New York Filed Dec. 2, 1958, Ser. No. 777,751

5 Claims. (Cl. 200-148) This invention relates to an operating mechanism for an electric switch, and, more particularly, to an operating mechanism for a switch which relies upon a jet of fluid to aid in extinguishing the usual arc which is established upon opening of the switch.

In certain switches of this general type, the above mentioned fluid jet is produced by a pneumatic device that is controlled by motion of a movable switch member, such as, for example, a contact blade. When the switch member reaches a certain point in its opening stroke, it initiates operation of the pneumatic device, and this causes a jet of fluid to be directed into the arcing region. A switch of this general type is disclosed and claimed in US. Patent No. 2,399,485-Harlow, assigned to the assignee of the present invention, and it is with a switch of this general type that we are particularly concerned.

An important consideration with a switch of this general type is that the path followed by the jet of fluid is dependent upon the speed of movement of the switch member, particularly, at the time the pneumatic device begins to operate. In this regard, if the switch member is moving below a predetermined speed during this interval, the path of the jet is in a direction leading into the usual arc chute, which is the most desirable direction from the standpoint of aiding in arc-extinction. But if the switch member is moving at a speed above this predetermined value, the jet is in a direction tending to bypass the arc chute, and this impairs the effectiveness of the jet in carrying out its intended function of driving the are into the arc chute.

With a manually-controlled switch-opening mechanism, the above consideration can be a significant problem, especially if there is a possibility that an operator will accidentally drive the switch blade at a speed above the predetermined value.

Accordingly, an object of our invention is to provide for such a switch a manually-controlled operating mechanism constructed in such a manner that it causes the fluid jet to be directed along a predetermined desired path irrespective of the speed at which an operator applies, or attempts to apply, switch-opening forces to the mechanism.

Another object is to insure that the jet has sufficient velocity to drive light current arcs, even as low as a fraction of an ampere, into the arc chute.

In carrying out our invention in one form, we provide an electric switch comprising means including a movable switch blade for establishing a circuit-interrupting arc. The switch also comprises an arc chute for aiding in extinguishing this are. For producing a jet of fluid to aid in driving the are into the arc chute, there is provided a pneumatic device operable in response to movement of said'blade through a predetermined point in a switchopening stroke. The pathfollowed by the jet and the velocity of the jet are dependent upon the speed of motion of the movable blade through an intermediate switchppening zone located immediately beyond said predeterice mined point. The path of the jet is directed into the arc chute and the velocity of the jet is sufliciently high to drive an arc of a fraction of an ampere into the chute only if the main blade is moving below a predetermined speed in this intermediate zone. A first operating member is coupled to the blade for transmitting switch-opening movement thereto. Overcenter spring means coupled to the first operating member is provided for driving the blade through continued switch-opening movement upon movement of the blade into said intermediate zone. Manually-controlled means is provided for transmitting switch-opening forces to said first operating member until said overcenter spring means becomes effective to drive said first operating member. During blade movement through at least the final portion of said intermediate zone, the manually-controlled means is rendered ineffective to transmit switch-opening forces to the first operating member. This allows the overcenter spring means to continue opening motion of the blade at a speed below said predetermined value irrespective of the speed at which operator attempts to operate said manually-controlled means.

For a better understanding of our invention, reference may be had to the following description taken in conjunction with the accompanying drawing, wherein:

Fig. 1 is a partially schematic view of an electric switch embodying one form of our invention. The switch is shown in its fully-closed position.

Fig. 2 is a view similar to that of Fig. 1 except that the parts of the switch are shown in an intermediate position through which they pass during the early stages of a switch-opening operation.

Fig. 3 also shows the parts of the switch in an intermediate position through which they pass during an opening stroke. The opening operation has reached a more advanced stage in Fig. 3 than in Fig. 2.

Fig. 4 depicts the parts of the switch at a still more advanced stage of an opening operation.

Fig. 5 illustrates a modified form of the invention.

Referring now to Fig. 1, there is shown an air circuit breaker or switch 10 of a type which is adapted both to interrupt load currents and to disconnect its associated circuit in the general manner of an air-break disconnect switch. This switch is of the general type shown and claimed in aforementioned Harlow patent. The switch comprises a pair of spaced-apart terminals indicated at 1 and 2 arranged to be interconnected in the normal closed-circuit position by a main current-carrying contact member 3. The contact member 3 is formed as a double blade contact that is secured to and mounted on a rotatable insulating shaft 4 for pivotal movement with respect to the upper fixed terminal 1.

Switch-opening is effected by rotating the shaft 4 in a clockwise direction to cause the blade 3 to move away from the fixed terminal 1, and switch-closing is effected by rotating the shaft in counterclockwise direction to cause the blade 3 to move from an open position counterclockwise toward the fixed terminal 1. The mechanism for effecting switch-closing can be of any suitable conventional type and is therefore shown at 5a in block form only. Preferably, it is of the type disclosed and claimed in our copending application S.N. 754,400, filed August 11, 1958, now Patent No. 2,914,635.

The mechanism fo effecting switch-opening is shown at 5. This mechanism 5 and its relationship to the rest of the switch form an important part of our invention and will soon be described in greater detail.

Referring still to Fig. 1, it will be noted that the upper terminal 1 has connected thereto a fixed contact structure including an arcing contact 6 and main currentcarrying finger-type contacts 7 arranged to be engaged by the blade 3. Also mounted on the fixed terminal 1 is an arc-extinguishing structure 8 comprising, in the illustrated switch, a'narrow arc chute of a suitable type hereinafter described. The arcing contact 6 is mounted within the arc chute for coaction with an arcingcontact 9, that is pivotally mounted on and carried by the main blade at 3a, whereas themain current contacts 7 are disposed exteriorly of the arc chute at opposite sides there: of, as indicated by the dotted lines of Fig. 1.

The arcing space or chamber within. the. arc chute comprises a narrow slot 11 that is open at the lower end of the chute for operationof the arcing contact 9 and also at the upper end at 12 for venting the arc gases. The sides of the are chute. are substantially closed and the. main part of, the. are chute is. provided with are extinguishing. bafile. structure. indicated at 13 for cooling, lengthening, and attenuating the arc stream as it moves upward into the chute. This movement of the arc is facilitated by'arcing horns located, at opposite ends of the arc chute, one of. which is conveniently formed by the f xed-arcing contact 6 and the other at 14 being close to the path of thearcingtip 9a of the arcing contract.

The arcingcontact is operatively related to the main blade so that when the shaft 4;is rotated clockwise from the position shown in Fig, 1 to open the circuit breaker, the main contacts at 3 and 7 first par-t contact and move apredetermined distance. toward open circuit position before partingof the arcing contacts occurs at. 6 and 9. Since the arcing contact 9 is electrically connected to the blade 3, the circuitbetween the terminals will be opened atthe arcing contacts rather than at the main contacts so that the arc tobe extinguished is drawn within the chute. 8 where it attaches to the arcing horns and is exti'nguished as it moves into the baflle structure.

The arcing contact.9 is latched so that it does not im: mediately or completely follow the blade 3 until the blade reaches. a predetermined position, whereupon the latch is tripped by means associated with the blade 3. When this occurs, spring biasing means, which had been stressed during the initial movement of the blade, snaps the arcing contact. awayfrom its fixed contact 6. Coincident with this operation, a strong jet of air is directed substantially transversely of the arc stream at the arcing contact so as to drive the arc upward within the chute, thereby to facilitate the interruption of large, as well as small, current arcs.

Specifically, the above results are brought about-by providing the arcing contact with alatching toggle I--16 that is arranged to be overset, as shown in Fig. l, and'resiliently held in an overset position by an overcenter spring 17. The upper end of the toggle link 15 is provided with a pin 18 guided for limited vertical reciproc al movement in a slot 1% formed in a lug 19a secured with respect to the arcing contact 9. The pin 18 also carries a roller 19 offset so as to be in alignment with a fixed catch 20 secured to the lower part of the arc chute along an edge thereof. The lower toggle link 16 is connected to a guide link 21 that is pivotally connected at 22 to the arcing contact and biased by a spring 23 in a counterclockwise direction so'as normally to hold the latching toggle 15-16 as a unit in its upper latching position.

For the purpose of controlling the latching toggle and for directing an air jet upward into the chute when the arcing contact is opened, a pneumatic device comprising a cylinder 24 and a piston25 is operatively connected to the arcing contact9 and to the main blade 3. In the specific arrangement shown, the cylinder 24, which is provided with an air jet nozzle 26, is mounted on and secured to the arcing contact 9. and coacts with the piston connected through its operating rod 27 to an offset portion of the main blade 3 at28. The pistonrod 27 clears the toggle 15, 16, but an adjustableextension 29 carried by the piston is arranged, so as to be substantially in alignment With theknee, or. central pivotfit! otithe toggle 15, 16. The toggle is held in the overset position shown in Fig. 1 by the spring 17 and a stop pin 31 that is arranged to be engaged by an extension of the link 16. Accordingly, when the knee of the toggle is moved sufiiciently over center toward the right the spring 17 causes collapse of the toggle so that the roller 19 moves downward in the slot 19b sufiiciently to clear both the catch 20.and:'the catch 20a.

A switch-opening operation will now be described. It will. first be assumedthat the switch is in the closed-circuit position shown, in Fig. 1 and that switch-opening is initiated by rotating the shaft 4. together. with blade 3 in a clockwise direction. During the initial clockwise opening movement ofthe main blade 3, the arcing contact 9 remains insliding. engagement with the fixed contact 6. Before the arcing contact 9 moves away from the fixed contact, however, the toggle latch roller 19 has engagedthefixedcatch 20. as. clearly shown by Fig. 2. S in ceth e toggle is still locked in its overset'position, further. immediate... movement of the arcing contact is restrained. The. blade, 3; continues to move clockwise stressing the arcing contact spring 9b and drawing with it. the piston 2 5,which, incidentally, is thereby positioned within the ..cylinder..24.in readiness for a working stroke, i.e., a jet-produoingstroke.

When the blade 3 has reached a predetermined posi-. tion in its.openingstroke where it is safe to open the arcing contact. without. danger of the arc restriking to the mainblade, the pistonextension 29v engages the knee of thetoggleand causes it to collapse as illustrated in Fig, 3. Asthetoggle collapses under influence of the spring 17-v thelatching roller 19 movesbeneath the fixed catch 20.so.as to release, the arcing, contact. Thereupon the arcing contact is snapped clockwise away from the fixed contact.6 by the. biasing spring 911; that interconnects the arcing and blade contacts as shown. This-snap actionof the arcing contact jquickly draws the arc across the lower endof the vchutefor transfer to the arcing horns.

thearcing contact 9 snaps open toward the blade 3, relative.rnovernentbetween the piston 25 and the cylirider 24 producesaworkingstroke of the piston as illustrated by Fig. 3 as so to force asharp and vigorous jet of air frornithe nozzle 26 upward into the arc chute soas toitrayerse .thearcstream at the arcing contact and force the. arc; upward along; thearcing horns into the chute, structure where it is extinguished. It will be noted, re; ferr g -tofig, 4, that the piston .25.closes off the nozzle opening 26 near the end of the working stroke. The, trappedair-at the left end of the cylinder therefore serves to cushion the. opening shock of the arcing contact 9.- Eurther opening movement of the breaker causes the arc,- ingand blade contactsv to move as a unit as indicated by. Fig. 4 to the complete open-circuit disconnecting position wherein the blade unit is in a substantially horizontal as tiqn o show Sincethe aboverdescribed jet is produced by relative. movementbetweenthe arcing contact 9 and the blade 3,- the path thatwill .be taken by the jet is dependent upon the, speed of motion of the blade, particularly during its travel through an intermediate zone in the opening stroke. just beyond the. point at which the arcingcontact is unlat ched. If vtheblade is moving through this intermediate zone at a relatively low, speed, then the path of the jet will be directed into the chute, as shown in Fig. 3. The higher. the speed of the blade during. its movement through-the crucial intermediatezone, the more advanced will be the-blade 3 when overtaken by the arcing contact 9,: and hence, the furtherto the. right will be the path of the-je If the speed is above apredetermined .value, thepath of thejet-will be so. far to the right asto, in etfect,bypass thearcchute. This will, of course, serious, ly impair theability of.the-jet to carry out -.its .intended function, i.e., driving thearcinto. the arc chute.

In accordance with the present invention, we.over.- comethiammblem by. constructing. .the switch-openin3 mechanism 5 in such a manner that it is incapable of driving the blade 3 at a speed above the above-mentioned predetermined value during the critical interval, as will be explained in greater detail hereinafter in connection with the detailed description of the switch-opening mechanism 5.

Even assuming that the jet is initiated while the main blade 3 is still passing throughv the crucial intermediate zone, if the speed of the main blade is excessive, the jet will have ins-utficient velocity and resultant strength to enable it to carry out its intended function. In this regard, the jet should have sufiicient velocity to drive an arc of even a fraction of an ampere into the chute, and the speed of the main blade should not exceed the value required to produce such a jet. Thus, the switch-operating mechanism 5 is further designed to drive the blade 3 during the critical interval at a speed no greater than the value required to produce a jet of sufficient velocity to drive an arc of even a fraction of an ampere into the chute. In connection with this latter feature, it is to be understood that, generally speaking, the smaller the arc, the stronger is the jet required in order to drive the are into the chute.

Referring now to the switch-opening mechanism 5, it will be noted that this mechanism comprises a driving cam 40 and a driven cam 41. The driving cam 40 is keyed to a rotatably-mounted actuating shaft 42, to which a switch-operating handle 44 is also keyed. The driven cam 41, on the other hand, is keyed to the operating shaft 4 of the switch. Also keyed to this operating shaft 4 is crank 45 which coacts with an overcenter tension spring 46. The tension spring 46 is secured at its upper end to the outer end of the crank 45 and its lower end to a stationary pin 48.

Switch-opening is initiated by manually pivoting the handle 44 in a counterclockwise direction from its position of Fig. 1. This rotates the driving cam 40 in a counterclockwise direction, causing it to engage the driven cam 41 and to begin driving this driven cam 41 clockwise from its position of Fig. 1. The crank 45, being coupled to the driven cam 41, is driven in unison with the cam 41 in a clockwise direction, thus tensioning the overcenter spring 46. When this aetion'has been continued sufficiently to drive the spring 46 overcenter relative to the shaft, the spring 46 discharges and drives the driven cam 41 ahead of the driving cam 40. Preferalby, the overcenter spring 46 begins to'discharge immediately after the parts of the switch have passed through their position of Fig. 2. The overcenter spring 46 continues to discharge until it has carried the blade 3 through the previously-m'entioned intermediate zone, in which it is depicted in Fig. 3, through the position of Fig. 4, and through still further travel into a fully-open position (not shown) which is almost horizontal.

The spring 46, in discharging, carries the driven cam 41 out of the path of movement of the driving cam 40 shortly after discharge of the spring 46 is initiated and while blade 3 is still located well within the crucial intermediate zone. When the driven cam 41 is so moved out of the path of the driving cam 40, the driving cam 40 becomes incapable of imparting further motion to the driven cam 41 irrespective of how fast the operator moves the driving cam 40. Even if the operator moved the driving cam at an extreme high speed, the opening speed of the blade 3 from this point on is governed almost entirely by the rate of discharge of the spring 46, and the spring is so designed that the opening speed is at the desired relatively low value. Thus, the possibility of the fluid jet being misdirected, or of its having insufiicient velocity, as a result of excessive blade speed is efiectively eliminated.

It will be noted that relative movement of the cylinder and piston from the position of Fig. 3 to that of Fig. 4 also causes resetting of the latching toggle to the original overset position shown by Fig. 1. Accordingly,

when the switch is to be closed, counterclockwise movement of the shaft 4 moves the reset contacts and pneumatic device as a unit toward the closed-circuit position. The closing duty, as Well as the opening duty, falls on the arcing contacts 6, 9, which close just prior to closing of the main contacts.

Switch-closing is effected by driving the shaft 4 counterclockwise through its position of Fig. 4 into its position of Fig. 1 by means of the switch-closing mechanism diagrammatically shown at 5a. As mentioned hereinabove, this switch-closing mechanism 5a is preferably of the type shown and claimed in our aforementioned copending application S.N. 754,400. It will be apparent from that application that a closing-operation cannot be initiated until the driving cam 40 has first been returned, or reset, to its position of Fig. 1. This resetting is accomplished simply by moving the handle 44 together with the driving cam 40 clockwise into their respective positions of Fig. 1. The driven cam 41, being out of the path of movement of the driving cam 40, as previously explained, does not interfere with this resetting of the driving cam 40. Thus, when the switch is subsequently closed, the driving cam 40 is in its position of Fig. 1 and is, therefore, in readiness to eifect another switch-opening operation.

Fig. 5 illustrates a modified form of our invention in which parts corresponding to those of Figs. 1-4 have been designated by corresponding reference numerals. In Fig. 5, the manually controlled means 40, 42 for transmitting switch-opening forces to the driven cam 41 is rendered ineffective at substantially the same point in the opening stroke as is the corresponding means 40, 42 of Figs. 14, but in a somewhat different manner. In this latter regard, movement of the driving cam 40 in a switch-opening direction is blocked by means of a stop 50 shortly after the driving cam 40 passes through a position corresponding to that of Fig. 3. When this occurs the driving cam 40 is no longer capable of imparting switch-opening movement to the driven cam. As a result, it is the overcenter spring 46 alone which is responsible for driving the main switch blade 3 through the critical portion of the intermediate switch-opening zone through which the blade travels after passing through the position of Fig. 3. The spring 46 drives the blade through this portion of the intermediate zone at a speed sufficiently low to insure that the jet of fluid from the nozzle 26 is directed into the arc chute 8 as was explained in greater detail hereinabove. The speed at which the spring drives the blade 3 is also low enough to insure that the jet has sufficient velocity to drive an arc of even a fraction of an ampere into the chute 8. In Fig. 5, the parts are shown in a position wherein the overcenter spring is driving the main blade through the crucial intermediate zone without the assistance of the driving cam 40, which had been disabled at an earlier point in the switch-opening stroke by the stop 50.

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

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

1. In an electric switch, means including a movable switch blade for establishing a circuit-interrupting arc, an arc chute for aiding in extinguishing said arc, means including a pneumatic device operable in response to movement of said blade through a predetermined point in a switch-opening stroke to produce a jet of fluid to aid in driving said are into said chute, the path followed by said jet being dependent upon the speed of motion of said blade through an intermediate switch-opening zone loeated immediately beyond said predetermined point, seesaw-using directedinto said chute "onlyif the blade ishoviiigbeloiva piedetermiried speed in at least a p'orion drama intermediate time, a first operating member coupled to said blade for transmit-ting switch openii'i'g 'r'nove'ment thereto, 'overeer'iter "spring means coupled "to said fir'st operating member fo'r driving said blade {through continued switch-opening movement "at a spee d below said predetermined value 'upon movenient of said blade into said ntermediate zone, a manuallycontroll'ed second operating fr n 'ei'riber fdr ti ansinittiri'g switch-opening "forces to said first operat iii'g member until said overcenter spring means becomes 'eflfeetive to drive 'said first operating member, said overceriters'pring means acting upon movement of said blade into said intermediate zone to drive "said first operating member out {of the path of moiiem'entof said second operating member so as to preclude said second operating memher from driving said fir'st operating member during movement of said blade through at least a final 'portio'n of 'said intermediate zone, the velocity of said jet being dependent upon the speed of said blade during blade movement through said intermediate zone, the velocity of said jet being sufficient to drive an arc 'of a fraction of an ampere into's'aid chute only if the speed of said blade is below '-a secondpredetermined'value in at least a" portion of said intermediate zone, said over-center spring means upon becoming effective acting to drive said blade at a speed below said s'econd predetermined value.

2. The switch of claim 1 in which said first operating member is a driven cam and said second operating member is a drivingcam engaging said driven cam duririg the t'ransmission'of switch-opening forces from the driving cam t'o'the driven cam, and in whichsaid overeenter spring upon becoming effective drives sa'id driven cam out of engagementwith 'saiddriving cam.

3. In --an electric switch, means including a movable switch blade for establishing-a circuitinterrupting arc, an arc chute for aiding in extinguishing said arc, means including a pneumatic device operable in response to movement of said blade through a predetermined point in a'switch-operiing stroke to produce a jet of fluid to aid in driving said are into said chute, the'path followed bysaid jet being dependent upon the speed of motion of said -blade through an intermediate switch-opening zone located -im'i'ri'ie'dia'tely beyond said predetermined point saiipat-hbein drre'cted him we chut'e only if the saac is moving below "a predetermined speed in at least a 'poi tionbf said intermediate z'o'ne, "'a' firs't operating member coupled to 'sa-i'd blade for transmittin 's'witch-open ing movement thereto, overcenter spring means coupled to said first operating member for driving said blade thfr'ongh-ecntmueH switch-bpening movement at a speed below saidiiredeterm ined value movement of said Blade into said intermediate zone, manually-controlled means for transmittingswitclr-opening forces to said first operating me'mbei' until "said over'center" spring means becomes effective to "diive sa id' first operating member, and means for rendering said manually coiitrolled means "inefiective 'to "transmit switch-opening "forces to said first operatingmember durii'ig hlademovement through at least the final portion of s'aid intefmediate fswitch-opening zone irrespective of'tlI'e speed of mdtio r 'of sa'id first operating member, the-velocity of said i'et' being dependent upon the speed of 'said' blade during blade movement through said intermeiditae zone, the velocity of said jet being 'sufliei'enttodr'ivean ar'c df'a fraction of an ampere into said chute only if the speed of said blade is below a predetermined 's'e'c'onh 'value in at least a portion of said intermediate zone, said *overce'nter spring means upo'n becoming effective aeting to drive said blade at a speed be'lo'vv said seeondp'red'etermined'value.

4. The switeho'i Claim? in which said means "torrend'erir'ig the manualIy-"controlled means inefiective com- "prises means for blocking switch-opening movement of 'saidii'ianually edntrolledinieans during movement of said blade at least through a final portion dfsaid intermediate zo'ne.

5. The switch of claim 4 in which said. first operating memberi's "a drivencam and said second operating memherisa drivingeam en agingsaid driven cam during the transmission of 'switch-'opening forces from the driving Cain-to the driven cam, and in which said over-center spring 'u'pon beeoming efieeti've 'dr ives said driven cam outof en'ga 'gem'e'nt'v'v'ith said driving'c'am.

Mason June 20, 1922 Haflowet a1. Apr. '50, 1946

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