US2956137A - Operating mechanism for an electric switch - Google Patents

Description

Oct. 11', 1960 c. H. ARCHER OPERATING MECHANISM FOR AN ELECTRIC SWITCH Filed Dec; 2, 1958- 3 Sheets-Sheet 1 INVENTOR. CLAUDE H.ARCHER. BY MAM 5244M dam-.

Oct. 11; 1960 c. H. ARCHER OPERATING MECHANISM FOR AN ELECTRIC SWITCH 3 Sheets-Sheet 2 Filed Dec. 2, 1958 INVENTOR. CLAUDE H. ARCHER :Oct. 11, 1960 c. H. ARCHER 2,956,137

OPERATING MECHANISM FOR AN ELECTRIC SWITCH Filed Dec. 2, 1958 3 Sheets-Sheet 3 INVENTOR. CLAUDE H. ARCHER United States Patent OPERATING MECHANISM FOR AN ELECTRIC SWITCH Claude H. Archer, Havertown, Pa., assignor to General Electric Company, a corporation of New York Filed Dec. 2, 1958, Ser. No. 777,678

3 Claims. (Cl. 200-146) This invention relates to an operating mechanism for an electric switch, and, more particularly, to improvements in an operating mechanism of the general type disclosed and claimed in application S.N. 777,751, Lester and Shaw, filed December 2, 1958, and assigned to the assignee of the present invention.

The operating mechanism disclosed in the aforementioned Lester and Shaw application comprises a pair of coacting cams that are relied upon for imparting switchopening movement to the movable contact member of the switch. After the driving one of the cams has been manually actuated to a predetermined point in a switchopening stroke, an overcenter spring takes over and thereupon completes the switch-opening operation independent 1y of the driving cam. In completing the opening operation, the overcenter spring separates the driven cam from the driving cam.

A disadvantage of this mechanism of the Lester and Shaw application is that it does not allow an operator to return the movable contact to its fully-closed position in the event that he decides against going ahead with an opening operation prior to actual interruption of the circuit at the usual arcing'contacts of the switch. The disengageable cams which are needed in order to allow the overcenter spring to perform independently of the operator are simply not suited to performing such a c1osing operation and can operate only in an opening direction.

Accordingly, it is an object of the present invention to provide a switch-operating mechanism which, in addition to allowing opening to be completed by a spring independently of a manually-controlled input member, enables an operator to utilize this input member for returning the main contact of the switch to its fuliy-closed position in the event that he decides against going ahead with an opening operation prior to actual circuit interruption.

Another object is to provide a mechanism capable of performing in the manner set forth in the immediately- I determined point in a switch-opening stroke. A first gear sector is coupled to the main contact for transmitting switch-opening movement thereto. Coupled to the first gear sector is an overcenter spring which drives the main contact through continued opening movement upon passage of the main contact through a point in the switchopening stroke located near said predetermined point. A manually-controlled second gear sector is provided for transmitting switch-opening forces to the first gear sector at least until-the overcenter spring takes over. The two ice gear sectors are disposed in meshing relationship at leastuntil the overcenter spring takes over, and this enables switch-closing forces, as well as switch-opening forces, to be transmitted from the second gear sector to the first at least until the overcenter spring becomes effective. The paths of movement of the gear sectors are such that shortly after the overcenter spring becomes effective, the sectors are moved out of mesh and remain out of mesh,

at least so long as said second sector is being urged in a switch-opening direction.

, For a better understanding of my invention, reference may be had to the following description taken in conjunction with the accompanynig 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. I

Fig. 3shows the parts of the switch in a more advanced intermediate position through which they pass during an opening stroke.

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

Fig. 5 depicts a modified form of my invention shown in a position corresponding to that of Fig. 2.

' 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 U.S. Patent No. 2,417,683, Harlow, assigned to the assignee of the present invention. The switch comprises a pair of relatively fixed terminals indicated at 1 and 2 arranged to be interconnected in the normal closedcircuit position by a main current-carrying contact memher 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 con-' ventional type and is therefore shown at 5a in block form only. Preferably, it is of the type disclosed and claimed in copending application S.N. 754,400, Lester et al., assigned to the assignee of the present invention and now Patent No. 2,914,635. The mechanism for 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 current-carrying 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 arcing contact 9 that is pivotally mounted on and carried by the main blade at 3a, whereas the main current contacts 7 are disposed exteriorly of the arc chute at opposite sides thereof, as indicated by the dotted lines of Fig. l.

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 operation of the arcing contact 9 and also at the upper end at 12 for venting the arc gases. The sides of the arc chute are substantially closed and the main part of the arc chute is provided with are extinguishing bafilestructure indicated at 13 for cooling, lengthening, and attenuating the arc stream as it moves upward into the chute. This movement of the are is facilitated by arcing horns located at opposite ends of the arc chute, one of which is conveniently formed by the fixed arcing contact 6 and the other at 14 being close to the path of the arcing tip 9a of the arcing contact.

The arcing contact 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 part contact and move a predetermined distance toward open circuit position before parting of the arcing contacts occurs at 6 and 9. Since the arcing contact 9 is electrically connected to the blade 3', the circuit between the terminals will be opened at the arcing contacts rather than at the main contacts so that the arc to be extinguished is drawn within the chute 8 where it attaches to the arcing horns and is extinguished as it moves into the bafile structure.

The arcing contact 9 is latched so that it does not immediately 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 away from 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 a latching toggle 15-16 that is arranged to be overset, as shown in Fig. 1, 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 reciprocal movement in a slot 19b 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 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 piston 25 is operatively connected to the arcing contact 9 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 25 connected through its operating rod 27 to an offset portion of the main blade 3 at 28. The piston rod 27 clears the toggle '15, 16, but an adjustable extension 29 carried by the piston is arranged so as to be substantially in alignment with the knee or central pivot 30 of the 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 suificiently to clear both the catch 20 and the catch 20a.

7 A switch-opening operation will now be described. It will first be assumed that the switch is in the closedeircuit position shown in Fig. 1 and that the switch- Since the toggle is still locked inits oversetposition,

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 25 which, incidentally, is thereby positioned within the cylinder 24in readiness for a working stroke,

i.e., a jet-producing stroke. I

When the blade 3 has reached a predetermined position in its opening stroke where it is safe to open the arcing contact without danger of the arc restriking to the main blade, the piston extension 29 engages the knee of the toggle and causes it to collapse as illustrated in Fig. 3. As the toggle collapses under influence of the spring 17 the latching roller 19 moves beneath 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 9b that interconnects the arcing and blade contacts as shown. This snap action of the arcing contact quickly draws the arc across the lower end of the chute for transfer to the arcing horns. As the arcing contact 9 snaps open toward the blade 3, relative movement between the piston 25 and the cylinder 24 produces a working stroke of the piston as illustrated by Fig. 3 so as to force a sharp and vigorous jet of air from the nozzle 26 upward into the arc chute so as to traverse the arc stream at the arcing contact and force the arc upward along the arcing horns into the chute structure where it is extinguished. It will be noted, referring to Fig. 4, that the piston 25' closes off the nozzle opening 26 near the end of the working stroke. The trapped air at the left end of the cylinder therefore serves to cushion the opening shock of the arcing contact 9. Further opening movement of the switch causes the arcing and blade contacts 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 position (not shown).

Since the above-described jet is produced by relative movement between the arcing contact 9 and the blade 3, the path that will 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 arcing contact is unlatched. If the blade 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 intermediate zone, the more advanced will be the blade 3 when overtaken by the arcing contact 9, and hence, the further to the right will be the path of the jet. If the speed is above a predetermined value, the path of the jet will be so far to the right as to, in effect, bypass the arc chute. This will, of course, seriously impair the ability of the jet to carry out its intended function, i.e., driving the are into the arc chute.

This problem is overcome in the mechanism of the present invention by constructing the switch-opening 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 through the crucial intermediate zone, if the speed of the main blade is excessive, the jet will have insufficient velocity and resultant strength to enable it to carry out its intended function. In this regard, the jet should have sufficient 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 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 sutficient 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 gear sector 40 and a driven gear sector 41. The driving gear sector 40 is keyed to a rotatably-mounted actuating shaft 42, to which a switch-operating handle 44 is also keyed. The driven gear sector 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 at its lower end to a stationary pin 48.

When the switch is fully-closed, as depicted in Fig. l, the driving sector 40 is located out of meshing relationship with the driven sector 41. To insure that the teeth of the two sectors will mesh when the driving sector 40 is rotated in a counterclockwise switch-opening direction from its position of Fig. 1, an adjustable abutment 49 is secured to the driven sector 41. This abutment is in the form of a stud threaded into a tapped hole provided in a rigid arm 50 fixed to the driven sector 41. A suitable lock nut 51 maintains the stud 49 in its desired position of adjustment. When the driving sector 40 is moved in a counterclockwise switch-opening direc tion, its front walls 40a first engages the stud 49. Continued movement of the driving sector is thereafter transmitted through the stud 49 to properly position the driven sector 41 in a position wherein its teeth mesh with the teeth of the driving sector.

Switch-opening is initiated by manually pivoting the handle 44 in a counterclockwise direction from its positon of Fig. 1. This rotates the driving gear sector 4G in a counterclockwise direction, causing its teeth to mesh with those of the driven gear sector 41, as above described, and to begin driving this driven sector 41 clockwise from its position of Fig. 1. The crank 45, being coupled to the driven sector 41, is driven in unison with the sector 41 in a clockwise direction, thus tensioning the overcenter spring 46. As shown in Fig. 2, when this action has been continued sufiiciently to drive the spring 46 overcenter relative to the shaft 4, the gear sectors have almost reached a point at which their teeth can no longer mesh, i.e., a point at which the last tooth on the driving sector 40 is ready to move out of engagement with the teeth of the drivensector 41. A slight amount of additional movement of the driving sector 40 in a switch-opening direction moves the driving sector 40 completely out of engagement with the driven sector 41 and, thereafter, the switch-opening operation is powered solely by discharge of the overcenter spring 46. Preferably, the sectors 40 and 41 are so proportioned that they disengage immediately after the point at which circuitopening motion of the arcing contact is initated, i.e., just beyond the position of Fig. 2. The overcenter spring 46 continues to discharge until it has carried the blade 3 through the previously-mentioned 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 driving sector 40 moves out of mesh with the driven sector 41 while the blade 3 is still located well within the crucial intermediate zone. When the driving sector 40 is so moved out of mesh with the driven sector 41, the driving sector 40 becomes incapable of imparting further motion to the driven sector 41 irrespective of how fast the operator moves the driving sector 40. The open ing 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 insutlicient velocity,'as a result of excessive blade speed is effectively 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 the aforementioned copending application S.N. 754,400. It will be apparent from that application that a closing-operation cannot be initiated until the driving sector '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 sector 40 clockwise into their respective positions of Fig. 1. When the switch is fully-open, the driven sector 41 is completely out of the path of movement of the driving sector 40, as will be apparent from Fig. 4, and therefore, does not interfere with this resetting of the driving sector 49. Thus, when the switch is subsequently closed, the driving sector 40 is in its position of Fig. 1 and is, therefore, in readiness to effect another switch-opening operation.

A particular advantage of the arrangement described up to this point is that it allows an operator to return the switch blade 3 to its closed position in the event that he decides against going ahead with an opening operation before the arcing contact 9 has been released to allow it to snap open. In this connection, if the operator had moved the main blade 3 from its position of Fig. 1 to some position between the position of Fig. 1 and that of Fig. 2 and had then decided against going ahead with the opening operation, he could return the main blade 3 to its fully closed position simply by returning the handle 44 to its position of Fig. 1. Such motion of the handle 44 causes the driving sector 40 to drive the driven sector 41 in a reverse or counterclockwise direction, and this returns the main blade 3 to its fully-closed position. The amount of power required for driving the main blade 3 into its fully closed position under such circumstances is relatively low inasmuch as the power circuit had remained closed during the partial opening operation immediately preceding return of the main blade 3 to its fully-closed position of Fig. 1. The circuit having remained energized, the inrush currents associated with closing a previously-deenergized circuit would not be present to oppose closing movement of the main blade 3. If it be assumed, on the other hand, that the circuit had been actually opened by the immediately preceding opening operation, a much greater amount of closing power might have been required in order successfully to return the main blade to its fully-closed position of Fig. 1. Under these latter circumstances, the operator would be forced to reestablish a power circuit that had been interrupted, and considerable opposition would be encountered from magnetic forces due to high inrush currents, especially if the power circuit were faulted when reclosure was attempted.

The arrangement of the present invention insures that an operator does not utilize the gear sectors 40 and 41 for an attempted reclosing of aninterrupted circuit. In this regard, the driving gear sector 40 moves out of mesh with the driven gear sector 41 almost immediately after the arcing blade 9 snaps. open. Theovercenter spring 46 then quickly completes the opening operation, and in so doing, drives the driven gear sector 41 completely out of the path of movement of the driving gear sector 40. Thus, should an operator attempt to effect a full closing operation by the act of returning the handle 44 to its position of'Fi'g. 1', no closing motion will be imparted'to the main blade 3. The driving gear sector 40 will simply move past the driven gear sector 41 without engaging the driven gear sector, thus imparting no motion to the main blade 3'.' r

In the arrangement described hereinabove, the overcenter spring is arranged to begin discharging shortly after circuit-opening movement of the arcing blade 9 has been initiated by tripping of the latching toggle 15 16. This means that the gear sectors 40 and 41 remain in mesh for aslight range of travel following the point at which circuit-interruption motion of the arcing contact 9 is initiated. This range of travel is so slight as to render it extremely unlikely that an operator will attempt to initiate a closing operation when the parts are positioned in this range of travel, but even thi's remote possibility is eliminated in a modified form ofmy invention by arranging the overcenter spring to become eifectiveat a point just ahead of the point at which the arcing contact is releasedto snap open.

Although I have described my invention particularly in connection with an arrangement wherein disengagement between the sectors is eifected by moving the driving sector out of meshing engagement with the driven sector, it is to be understood that disengagement can equally well be eifec'ted by'having the overcenter spring move the driven sector out of engagement with the driving sector. Such a modified arrangement is depicted in Fig. 5, where those parts corresponding to similar parts in Figs. 1-4 have been assigned the same reference numerals. In Fig. 5, the parts of the modified switch are shown in a position corresponding to that of Fig. 2. When the driving gear sector 40 is moved clockwise'slightly beyond its position of Fig. 5, the overcenter spring moves the driven sector 41 out of engagement with the driving sector 40 and also out of the path of movement of the driving sector 40. This renders the driving sector incapable of imparting further opening movement to the blade 3, allowing opening movement thereafter to be powered solely by the overcenter spring and independently of the driving sector 40 irrespective of how fast the operator moves the driving sector 40.

The switch of Fig. also includes a gear-positioning device 4951 for cooperating with the front wall 40a of the driving sector 40 to insure that the gears mesh properly when the driving sector 40 is moved from a position corresponding to that of Fig. 1 toward the position in which it is depicted in Fig. 5. The positioning device 4951 operates in the same general manner as described hereinabove in connection with the,similarly-designated position device of Fig. l.

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

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

1. In an electric switch, a movable main contact, a movable arcing contact, means controlled by switchopening movement of said main contact for effecting circuit opening movement of said arcing contact after said main contact has been moved through a predetermined point in a switch opening stroke, a first gear sector coupled to said main contact for. transmitting switchopening movement thereto, overcenter spring means coupled to said first gear sector for driving said main contact through continued switch-opening movement upon movement of said main contact into a predetermined intermediate position in a switch-opening stroke located near said predetermined point, a manually-controlled second gear sector for transmitting switch-opening forces to said first gear sector at least until said spring becomes effectiveto drive said first gear sector, said gear sectors being disposed in meshing relationship at least until said overcenter. spring becomes effective, thereby enabling switch closing forces to be transmitted from said second gear sector to said main switch blade at least until said overcenter spring becomes effective; the paths of movement of said gear sectors being such that shortly after said overcenter spring becomes effective, the sectors are moved out of mesh and remain out of mesh so long as said second sector is being urged in a switch-opening direction.

2. The arrangement of claim 1 in which said over center spring means, upon becoming effective, drives said first gear sector into a position out of the path of movement of said second gear sector, whereby said second gear sector is rendered inefiective to transmit closing forces to said main contactmember after a circuit inter rupting operation.

3. The arrangement of claim 1 in which said predetermined intermediate position is located at a point in the opening stroke slightly ahead of the predetermined point at which circuit opening movement of said arcing contact is initiated.

References Cited in the file of this patent UNITED STATES PATENTS 393,828 Hall Dec. 4, 1888 1,402,157 Gardner Jan. 3, 1922 1,420,382 Mason June 20, 1922. 1,797,490 Wilson Mar. 24, 1931 2,399,485 Harlow et al Apr. 30, 1946

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