US1839083A - Electric switch - Google Patents

Description

' Dec. 29, 1931. G. A. BURNHAM 1,839,083

ELECTRIC `swITpH Filed July 28, 1928 Patented Dec. 29,` 1931 UNITED -.P,a'rlgfflqf'l'i` Aenuncia: A. BURNHAM, or sUGUs, MASsAcHusETTs,

f OFFICE y AssIaNoa To coNDIT nr.ii;c :TnmALI 'MANUFACTURINGl CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPORA-A i TIoN oF MASSACHUSETTS kELEcTaIc SWITCH l Application tiled 4July 28, 1928.` Serial No. 295,905.

This invention relates to electric switches or circuit breakers and has particular refer ence to the stationary and movable arcing contact members which cooperate to interrupt the current flowing through the circuit. f f

Various devices have been employed to assist` in extinguishing the circuit interrupting arc drawn between the separatingv contact members, but most circuit breakers depend primarily upon the quick separation of the contactrmembers themselves, whereby the arc is rapidlyV attentuated and becomes so unstable that it goes out. vParticu-V larlyv in'oil immersed ycircuit breakers, it is considered imperative that thel arc be'extinguished as quickly as' possible since its presence in the oil-causes rapid decomposition rthereof into inflammable gases. andv vapors. Consequentlyit is the ractice to operate the movable switch mem er with great rapidity either by gravity and inherent resihence of thel contacts or by powerfulV acceleratingsprings associated with the operating mechanism. "Particularly in the latter case, some means must be provided to absorb the energy of the movable switch member at the end of its opening stroke, and to this end resilient bumpershave been provided for the switch member, or decelerat-v ing springs havebeen laced jin the .operating mechanism. The orrnerremedy l1s objectionable due to therebound which tends to cause the reiestablishment of the arc, while the latter has a tendency to retard the switch member before the arc has been extinguished.

A circuit breaker is sometimes calledupon to interrupt a current many times its normal rating, due to a short circuit or some lother severev overload condition, and the arc betweenk the `contacts may persist and cause thel destruction ofthe contacts. Particularly in the case of oil immersed circuit breakers the damage may be very.' great due to the generation of Vinflammable oil gases and vapors, and a destructive explosion -may result from'a ersistence of the arc after the contacts are ully separated. c .y

\ It is an object of the present inventionto provide a circuit breaker wherein the 'sep-V i arable contacts are separated, preferably at the latter part of the switch opening movement, and when the arc is already attenuated and unstable, at a speed whichV is hi her than that of, and is due to, the speed o the movable switch memberthus to extin ui'sh an arc V.which might otherwisel persistl ora substantial period of time.

It is Va further object of the invention to providefmeans for utilizing the surplus energy` of the movableswitch member. at `the end of its switch opening movement to enhance the extinguishment of the circuit `interrupting arc, and specifically toy utilize theenergy of the movableswitch member Y out appreciable rebound.

A still further object is generally to improve the construction and performance Vof electric circuit breakers. ,y

Fig. l is av sectional. elevationl of an oil immersedl electric switch or circuit breaker embodying the invention. K

Fig. 2 is a sectional elevation of the switch taken onlines 2-2 of Fig; 1.

Fig. 3 is a perspective view of the supporting bracket for the movable arcing contact members. i f Y l i Fig. l4r is a perspective view of a contact supporting arm for an arcing contact memf Fig. 5 is a detailshowing the springV assosupporting bracket of Fig. 3. As herein shown, the electric switch lem,- bodying the invent-ion includes a switch `ciated with Ythe contact arm of Fig. 4' and the frame 10 adapted to provide a cover for the' vin which the cooperating stationary and movable contact members of the switch are immersed.

Stationary switch members are supported by said switch frame 10 and depend therebelow into the oil in said receptacle 12 and include the porcelain insulating bushings 14. which enclose axial conducting studs 16. Said studs extend beyond the lower ends oil said bushings and are screw-threaded at their lower extended ends into the stationary main contact members or blocks 18.

Stationary auxiliary contacts or arcing members 19 are provided adjacent said main Contact blocks and are secured in conducting relation with said bloclr and held i'ixedly in position thereagainst by means of screws 19a.

The movable switch member includes the insulating switch opera-ting` rod 2O which is adapted to carry the main and auxiliary movlable contact members at its lower end in position to engage the stationary main and auX- iliary Contact members 18 and 19 and complete the circuit through the switch. A metal rod 22, secured to said insulating rod 2O at its upper end, is operatively connected to suitable switch operating mechanism (not shown). At its lower end said rod 20 is provided with an enlarged portion 23, preferably ot metal, to which the main movable brush Inember l24 is removably secured by means of a U-shaped metal clamp 25 having the upstanding ends 26 which are adapted to closely receive the laminations of the movable contact, or brush, 24 therebetween. A pin BO extends through the upstanding vends 26 of said U-shaped clamp and the enlarged portion 23 of said switch operatingr member whereby said brush is removably secured to said operating rod 20, and fasteners 32 serve to secure the laminations oi'v the brush or bridging member 24 to the bottom of said U- shaped clamp 25.

The U-shaped clamp 25 is further provided with opposed outwardly anddownwardly extended arms, or brackets, 34, Fig. 3, which are arranged to support the movable auxiliary contact or arcing members therebeneath. To this end said arms Set are each provided with a pair of spaced depending ears 36 at their free outer' ends upon which contact supporting frocker arms 38 of the auxiliary contact members are pivotally supported by pins Ll0. As shown in detail in Fig. l, said contact supporting arms 38 are of channel section and are provided with supporting ears Ll2 intermediate their ends by whi-ch they are pivotally supported on the pins Zl() between the ears 3G of said brackets 34. Contact or arc- ,ing members 14 are secured detachably by screws 47 to the outwardly directed upturned ends 118 of said supporting arms 3S in position to cooperate with the stationary contacts 19.

Said arms 38 Vare further provided Withintegral inwardly extended arms 50 the upturned ends of which are disposed side by side or overlap each other at a point beneath the middle of said U-shaped clamp 25. Said arms i0 preferably have struck out portions 5l at their overlapping ends as shown in Figs. 2 and d, so that both arms are free for vertical movement without interference trom the other.

Means are provided constantly to bias said contact supporting arms 38 in an upward direction against the ends 52 of the brackets 34, which act as abutments to limit the upward movement of the arcing contact members. v Said means comprise the constantly stressed cantilever springs Sil which encircle the pins 40, one end of each spring passing through said .pins 4() and the other end eX- tending beneath and bearing against an arm 8S, as shown in Fig. 5. The movable arcing contact members 44 are consequently urged against their cooperating contacts 19 when the switch is in closed position, and due to the above resilient support are caused to remain in contact therewith for a sufficient time subsequent to the separation of the main brush member 24.- to prevent arcing at the main contacts and brush members.

Then the operating rod 20 is moved downwardly to open the switch, an arc is drawn between each pair of auxiliary contact members 19 and 14 and it attenuated by the downward movement ol the movable switch member, the opening speed of which is enhanced by an accelerating spring 45, surrounding the rod 22. Under normal conditions'the arc will become unstable and go out before the movable switch member has reached the end of its opening stroke, but under heavy overload conditions the arc between the auxiliary contacts 19 and 44 may persist after the movable switch member has reached the end ot opening stroke and may, unless extinguished, cause the destruction ot' the switch.

According to the invention, means are provided to eiiect, during the final opening movement of the switch member, an extent of separation of the arcing members which is greater than the stroke of the movable switch meinber, and a speed of separation which is materially greater than the speed o opening movement of the movable switch member. To this end a resilient bumper provided directly beneath and in axial alignment with said movable operating rod 20, which bumper is arranged to engage the tips of the inwardly directed overlapping arms 5() of said contact supporting arms 3S prior to the end of the opening stroke of the movable switch member.` `Said bumper as here shown includes a piston 5G having an upstanding stem 58 which is axially aligned with the operating rod2() and hence directly beneath the adjacent struclr-out ends of `arms 50, an enclosing casing 60 for said piston, and a helical compression spring 62 disposed within said casing'beneath'said piston and in position constantlyto bias said piston in an upward direction. -Said casing is suitably supported in fixedposition ras byv being secured by bolts 64f`to andbeneath a cross vbar'66 whichfextendsacross the centre of the switch casing 12 perpendicular to the bridging member `24.V

Uprights 68 preferably of insulating material extendy upwardlyfrom said cross-bar in position to be secured removably by boltsV 70 toa pair of suitably spaced depending ears 72 whichmay be formed integral with the switch frame 10.` y

As the movablefswitch member nears the end of its switch opening movement, the arms -engage the stem' 58, and sincethe spring 62 beneath thepiston 56 is relatively stitfcompared Awith the springs 54 of the auxiliary contact members, the springs 54 yield the most andcause the contact supporting arms 38 to rotate about pins 40 to effect a Afurther and rapid separation of the arcing contacts towards the lower Vdotted line position of F ig. 1. The spring 62 is initially compressed upon the' engagement of the stem 68 and arms 50 and absorbs enough of the energy'of the switch opening movement to prevent injury to the mechanism, and reacts immediately to continue the downward and outward movement of the movable arcing tips 44.

It will be noted Athat during the opening movement of the switch into the intermediate dotted position of Fig. 1, 'prior tothe engagement of the stem 58 with the arms 50, the arcing members 44 are moved ina uniform vertical path away 'from their cooperating contacts 19, while the subsequent movement ofthe'contacts 44 due to the pivotal movement of arms 38 about their supporting pins 40, is at an Vangle to this path and to y the axis of the existing arc. lThe location of the pivot pointsl of' the contactv supporting members `38 is such that a Asmall linear movement of the arms' 50 causes a considerably greater linear movement of the outer arms 48 on which' the arcing contact members are carried; so that the rapidniovement of the movable switch member against the bumper, due to the accelerating spring and the force of gravity, causes the arcing tips to be moved downwardly through'the oil'suddenly and at an angle to the axis of the existing arc into the lower dotted position of Fig. l', and any arc whichy may have persisted willbe caused to go out, the arcing member 44 being snapped away from the-foot of the arc as well `as being laterally displaced therefrom' in the he work performed in moving the Contact bearing arms 38 suddenly through the 'oil against the bias of springs 54 is considerable and consequently the force of the movable switch member is'dissipated without'any l'appreciable reaction. The spring 62 beneath the piston serves largely to protectthe movable the stem 58 andbeing relatively rigid will react before the end ofthe switch opening l stroke of the switch member. v

f The uprights- 68 which support the bumper are arranged to be vertically adjustable to var-y the point in the switch opening movement at which the bumper will operate to snap the, arcing 'contacts apart. To this end a series of vertically aligned holes 7 4 are'pro- `vided in the uprights 68through any of which the bolt 7 0 may be inserted.

Although I have disclosed the invention 'as embodied in an oil immersed electric switch it is equally applicable to air-break switches and various modifications in the structure may be ade without departing from the scope of this invention.

Iclaimz' Y H 1. In `an electric switch,fthe combination of a stationary switch member, a movable switch member having an arcing member which is movable therewith' and which'cooperateswith saidV stationary switch member, and means effective only during the later part of the opening `movement ofthe movable switch member and after said arcing member has been moved at the velocity of opening movement of'saidmovable switch member a substantial distance out of engagement with said stationary switch member to move said arcing member further in a direction away from said stationary switch vmember at a rate of speed which is greater than the opening speed of said arcing member due to the speed of saidmovable switch member. Y .2.: The method of interrupting an electric arc which consists in initially elongating it at a suitablerate and `then in suddenly elongating it at a materially increased rate.

3. The method of interrupting an electric yarc which consists in elongating itat a suitable rate until it becomes unstable and thereupon continuing its elongation at a materially increased rate. Y

4. In an electric switch, the combination of a stationary switch member,v a movable switch member, a pivotally mounted arcing member carried by themovable switch member and engageable and disengageable with said stationary switch member, and means cooperating with said movable switch member and effective onl after the karcing member has moved a su stantial distance away fromsaid stationary switch member to rotate said arcing member ab'outits pivot in aswitch opening direction during and by the switch opening movement of they switch. 5. In an electric switch, the combination of a pair of stationary switch'members, a movable switch member, a pair of pivotally switch opening speed thereof out of engagement, with and into a position remote from said stationary switch member, and means cooperating with said movable switch member near the end of its switch opening movement constructed and arranged to engage said movable switehmember and rotate said areing members about their pivots in a switch opening direction during the final switch opening movement ot' said movable switch member and at a speed greater than the speed of said arcing members due to the opening speed of said movable switch member.

6. In an electric switch, the combination of a switch member which is movable between switch open and closed positions, a stationary switch member, an arcing member pivotally carried by said movable switch member, and means operated by the opening movement of said movable switch member to engage and move said arcing member about its pivot in a switch opening direction only during the final part of the switch opening movement.

7. In an electric switch, the combination of a movable contact member, a stationary contact member, an auxiliary contact supporting arm carried by said movable contact member and movable in respect thereto, an arcing member carried by said arm, and means normally operatively free Jfrom but engageable with said arm during the linal part only of the opening movement of said movable contact member to move said arcing member in a switch opening direction and at a speed in eX- cess of the speed oi said arcing member due to the opening speed of said movable contact member.

8. In an electric switch, a stationary switch member, a cooperating movable switch member, means to separate said members at a given rate, and other means operative after said members have been separated a given distance to increase the rate of separation of said switch members.

9. In an electric switch, a stationary switch member, a cooperating movable switch member having a pivotally supported arcing tip movable between switch open and closed positions, and means disposed in the switch opening path of movement of said movable switch member and normally operatively free from said switch member arranged to engage and rotate said moving arcing tip about its pivotal support in a switch opening direction only after said arcing tip has moved a given distance.

10. In an electric switch, a stationary switch member, a cooperating movable switch member, an arcing contact member having a movable support on said movable switch member and movable therewith into and out of switch clos-ing position, and a relatively fixed abutment normally operatively free from and disposed in the switch opening path of `movement of said movable switch member in position to engage and move said arcing contact member about its movablesupport in a switch opening direction during the final part of movement only of said movable switch member.

11. In an electric switch, a movable switch member including a switch operating rod, and a pivoted contact member movable therewith into and out of switch closing position, and a resilient bumper disposed beneath said movable switch member in position to engage said contact member' and rotate it about its pivotal support in a switch opening direction during the movement of said switch member int-o switch open position.

l2. In an electric switch, the combination of a movable switch member including a reciprocable switch operating rod, a main Contact member disposed at the lower end of said rod, a downwardly and outwardly extended bracket carried by the lower end of said rod, a contact supporting member pivoted to the extended end of said bracket and having a relatively long contact supporting arm and a short striker arm, an arcing tip carried at the extended endofsaid Contact supporting mem* her, and a relatively fixed abutment disposed beneath said movable switch member in position to engage said striker arm at the end of the switch opening movement of said movable switch member.

i3. In an electric switch, the combination oiE a movable switch member including a reciprocable switch operating rod, a main contact member disposed at the lower end of said rod, a downwardly and outwardly extended bracket carried by the lower end ot said rod, a contact supporting member pivoted to the extended end of said bracket and having a relatively long contact supporting arm and a short striker arm, an arcing tip carried at the extended end of said contact supporting member, and a relatively fixed abutment disposed beneath said movable switch memller in position to engage said striker arm at the end ot the switch opening movement ot' said movable switch member whereby said arcing tip is snapped downwardly and outwardly by the rotation of said contact supporting arm about its pivotal support on said bracket.

lll. In an electric. switch, the combination oi" a pair of spaced stationary switch members, a movable switch member cooperating therewith, al pair or' pivotally mounted arcing contact members carried by said movable switch member, and means to prevent a rebound of said movable switch member at the end of its switch opening movement includa resilient abutment disposed in thel path of movement thereof and in position tov engage and move said arcing contact members rapidly about their pivotal. support in a switch opening direction, whereby to absorb the energy of switch opening movement oit' said movable switch member.

15. The method of interrupting an electric circuitV which consists in drawing an arc, attenuating the arc until the arc reaches a stage where it becomes unstable, and causing Athe arc to go out by suddenly increasing the rate of attenuation of the arc.

16. The method of interrupting an electric circuit which consists in drawing an arc between two cooperating contact members, separating said contact 'members substantially in a straight line to attenuate the arc and cause it to become unstable, and subsequently causing one of said contacts to move Y suddenly further away from its cooperating Contact member and at an angle to the previous line of separating movement thereof.

17. The method of interrupting an electric circuit which consists in establishing an arc in an arc quenching fluid, attenuating said arc slowly in a uniform path until said arc becomes unstable, and then rapidlyy attenuating said arc and simultaneously displacing laterally of said path in the arcquenching uid.

18. The method of interrupting an electric switch which consists in establishing an arc between two cooperating arcing Contact members and beneath an arc quenching fluid, drawing the arc out by separating said contact members ina uniform path, and finally moving one of said contact members with a snap action at an angle to. said first path of movement, whereby to further attenuate the are and also to snap said contact member lat-v erally away from the foot of the arc.

19. The method of operating an electric switch of the type having a movable switch member and an arcing member movable on said switch member, which consists in arrestingthe opening movement of the movable switch member in the latter part only of its switch openingmovement and utilizing the energy thereof in moving the arcing member in a switch opening direction.

20. In an electric switch, engageable and disengageable Contact members, andrmeans to separatel the disengaged contact members at a given rate including means effective only after a given extent of separation to suddenly increase the rate of separation of said contact members.

In testimony whereof, I have signed my name to this specification.

GEORGEV A. BURNHAM.

Images