US3132225A

US3132225A - Electric switch having arcing and current carrying contacts of bridging type

Info

Publication number: US3132225A
Application number: US133484A
Authority: US
Inventors: Merle R Swinehart
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1961-08-23
Filing date: 1961-08-23
Publication date: 1964-05-05
Anticipated expiration: 1981-05-05

Description

May 5, 1964 M. R. SWINEHART ELECTRIC SW ITCH HAVING ARCING AND CURRENT CARRYING CONTACTS OF BRIDGING TYPE 6 Sheets-Sheet 1 Filed Aug. 23, 1961 IF iw Q: Q. a H 2 3 d n A I|||H 1 11R. H 0$ 8. H T 6 N u w 33 II (in I m H 3 m3 N 33 uw mum May 5, 1964 M. R. SWINEHART 3,132,225

ELECTRIC SWITCH HAVING ARCING AND CURRENT CARRYING CONTACTS OF BRIDGING TYPE 6 Sheets-Sheet 2 Filed Aug. 23, 1961 mom wu #m mom mm s 3 fl 9 M I Q0 m 1 0M 0Q H 3m 3m mm mm u w 10m Q I mum M y 1964 M. R. SWINEHART 3,132,225

ELECTRIC SWITCH HAVING ARCING AND CURRENT CARRYING CONTACTS OF BRIDGING TYPE Filed Au hza, 1961 6 Sheets-Sheet C5 y 5, 1964 M R. SWINEHART 3,132,225

ELECTRIC SWI'ICH HAVING ARCING AND CURRENT CARRYING CONTACTS OF BRIDGING TYPE Filed Aug. 25, 1961 6 Sheets-Sheet 4 May 5, 1964 M. R. SWINEHART 3,132,225

ELECTRIC s TCH HAVING ARC AND u T CARRY CONTACTS OF BR ING Filed Aug. 25, 1961 6 Sheets-Sheet 5 y 5, 1964 M. R. SWINEHART 3,132,225

ELECTRIC SWITCH HAVING ARCING AND CURRENT CARRYING CONTACTS 0F BRIDGING TYPE 6 Sheets-Sheet 6 Filed Aug. 25. 1961 United A States Patent.

This invention relates to electric switches and more particularly to electricswitchesadapted for controlling large values of electric energy.

While not limited thereto, the inventionis especially applicable to electromagnetic contactors for railroad locomotive service or the like wherein it is necessary to control and inteirupt high electric currents. I

7 An object of the invention is to provide an improved electric switch for controlling high values of electric power.

A more specific object of the invention is toprovide an improved electric switch of the bridging contacts type.

Another specific object of the invention is to provide an improved electric switch having arcing contacts of the bridging type and current carrying contacts of. the bridging type to afford establishment of and interruption of an electrical connection in two places in series thereby to enable control of higher power connections.

Another specific object of the invention is to provide improved arc horn means for an electric switch.

Another specific object of the invention is to provide improved arc shield means foran electric switch.

.A further specific object of the invention is to provide improved arc shield means having means to prevent arc damage thereto and affording more effective'insulation between the stationary and movable contacts.

Other objects and advantages of the invention will.

hereinafter appear. t

e The above mentioned and other objects and advantages of the invention and the manner of obtaining them will best be understood by reference to the following detailed description of anexemplary embodiment of an electric switch taken in conjunction with the accompanying draw ings, wherein: p

FIGURE 1 is a front elevation view of an electrical contactor constructed in accordance with the invention;

FIG. 2 is a right side elevation view of the contactor ofFIG. 1; t

FIG. 3 is a cross-sectional view, taken along line 3-3 of FIG; 1;

FIG. 4 is an exploded view of a portion of the contactor of FIG.'1; p v

FIG. 5 is an exploded view of another portion of the contactor of FIG. 1; H

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 1;

FIG. 7 is a cross-sectional view; of one side portion of the contactor taken along line 7-7 of FIG. 2;

FIG. 8 is a cross-sectional view of the taken along line 8-8 of FIG. 2;

FIG. 9 is a cross-sectional view of the portion of FIG. 7 taken along line 9-9 of FIG. 2;

H6. .10 is an isometric view of a member constituting one-half of an arc shield showing the interior structure thereof; and

viewed'ifrom another direction.

Referring to FIGS. 1 and 2, there shown a mounting panel or base 2 of electrically insulating rnaterial for FIG.-1'l is an isometric view of the member of 'FIG. '10

supporting the contactor, the parts of the contactor being 1 secured to the front surface asshown in FIG. 1 and to the portion of FIG. 7

left-hand surface of the panel as shown in FIG. 2 by bolts and screws extending into and through the panel. I

The contactor is provided with an electromagnet comprising a coil 4 having terminals 4a and 4b and a core '6 of magnetic material extending therethrough and rigidly secured to panel 2 and a pivotal armature 8 of magnetic material. The electromagnet is provided with means accessible from the front of panel 2 to alford ready re. moval of coil '4. l'lhis means comprises a washer 6a of larger diameter than the axial hole in the coil for maintaining the coil on the core, a screw 6b or the like threaded into an axial tapped hole in the free end of the core for retaining washer 6a in place and a slightly concave or dish-shaped relatively fiat resilient spring washer 6c interposed between washer a: and coil 4 with the concave side thereoftoward the coil for pressing the coil against its supporting bracket hereinafter described.

An L-shaped bracket 10 has the face of one angular portion dtla arranged in parallel abutting relation to the lower portion of the front surface of panel 2 and another angular portion ltlb extending horizontally fnom'the lower edge of the panel. A screw 12 extends through a suit-- able hole in base 2 and a corresponding-hole 10c (FIG. 4) in angular portion 10a into threadedengagement in an axial tapped hole in the other end of core ti to rigidly secure the core and bracket to the panel. Another screw 14 (FIG. 2) offset from screw 12 extends through a suitable hole in panel 2 into threaded engagement in a tapped hole ltld (FIG. 4) in angular portion 10a to prevent rotation of bracket 10 on screw 12.

As shown in FIGS, 2, 3 and 4, angular portion ltlb of bracket 10 is provided with means afiordin'g a pivotal seat for armature 8 comprising a transverse bar 16- rigidly secured, as by welding, across the upper surface thereshown in FIGS. .2 and 3 is mounted on the upper surface of the extreme end of angular portion ltlb of bracket 10 for use in electrical interlocking or auxiliary circuits or the like. t Y

As in'FIGS. 2, 3 and 4, armature 8 is ct general ly flat configuration and is provided across its lower edge with an acute angular portion forming an elongated sharp edge 8a for pivoting in the substantially right angle between bar 16 and portion 10b of the bracket. This long pivot edge prevents wear at the armature pivot. Arma ture '8 isconfined against lateral movement by a pair of pins 16a extending from bar 16 on opposite sides ofthe lower end of the armature. A dust seal 16b of resilient or foam like rubber material is cemented along the upper surface of bar 16. Seal t16b has its edge pressed into engagement with the right-hand surface of armature 8 to seal the armature pivot from admission of dust or the like. A projection or plate 8b extends horizontallyatl a substantially right angle from the face of armature 8' adjacent the lower end' thereof and is provided with a pair of enlarged, spaced holes '80 for freely accommodating bolts l3 when the armature pivots. Holes'Bc are provided with counter bores as shown-in FIG. 4 for accommodating resilient armature return means such as the lower ends of helical compression spnings 22 surround-ing the respective bolts. The upper ends of \spn'nrgs 22 are stopped against suitable washers 18a which are held in 3 place by nuts 18b threaded on the end-s of the bolts as shown in FIG. 3. SpringsZZ apply a force near the end of projection 8b at a small angle relative to the major axis or plane of the armature when the armature is open and bearing against its stop hereinafter described thereby maintaining pivotal edge 8a of the armature biased against bar 16 and in its seat. A lever or 8d extends from plate 8b at an upward angle and is provided through its free end with an adjustable bolt for engaging actuator 29a (FIG 1) for operating switch 20 when the armature is actuated. Armature 8 is further provided with a threaded stud 8e extending horizontally froman upper portion of the left-hand surface thereof as shown in FIG. 4 for securing thereto a movable contact assembly hereinafter described.

As shown in FIGS. 1, 3 and 5, a pair of stationary contacts 2.4 and 26 are rigidly secured in spaced apart relation through respective terminal members hereinafter described to mounting panel 2. Each such stationary contact is comprised of electrically conducting materials such as copper or the like and comprises a generally horizontal U-shaped configuration having an upper leg 24a, 26a and a lower leg 24b, 26b. The ends of lower legs 24b and 26b abut against respective terminal members 28 and 30 and are rigidly secured thereto by

screws

32 and 34 extending through the respective terminal members to provide electrical connections. Upper legs 24a and 26a are shorter than lower legs 24b and 26b and the ends thereof are spaced from terminal members 28 and 30 electrically to insulate the same from the terminal members. Electrical connection of the terminal members to the lower legs of the stationary contacts affords current flow in directions to aid blowout of the arcs as hereinafter more fully described.

Screws

32 and 34 extend through holes in terminal members 218 and 30 into threaded engagement in tapped holes extending axially into lower legs 24b and 26b. Terminal members 28 and 30 have

first portions

28a and 30a extending upwardly along the face of panel 2 and second angular portions 28b and 30b extending over the upper edge of panel 2 beyond the rear surface of the panel. Portions 28b and 3% of the terminal members are provided with suitable electrical connectors 28c and 300 for connecting electrical conductors thereto.

Means are provided which are accessible from the front of panel 2 to afford ready removal of the stationary contacts. These means comprise terminal-s members 28 and 30 secured to panel, 2 by pairs of

screws

28d, 28a and 30d, Sile extending through holes in the upper and lower ends of

portions

28a and 30a of the terminal members and through corresponding holes in the panel into threaded engagement with suitable threaded sleeve inserts 2a pressed into the panel from the rear face thereof. As will be apparent, screws 28d, 282 and 30d, Site are accessible from the front face 2b of the panel to facilitate removal of the stationary contacts and terminal members when panel 2 is secured tosupporting structure.

. 'Ihe lower portion of the yoke portion of each horizontal Ushaped stationary contact is provided on its outer surface with a recess filled with an arcing contacting member 24c, 260 as shown in FIGS. 3 and 5. Immediately below such contacting member, there is provided downward projection 24d, 26d having a deeper recess partially filled with a current carrying contacting member Z4e, Zoe. These contacting members are comprised of metal such as silver or the like having good electrical conducting properties. The step-like discontinuity between such contacting members on each stationary contact affords closure and opening of the arcing and current carrying contacts in the proper order as hereinafter described.

tAS shown in FIGS. 2, 3 and 5, the windows formed by the U-shaped stationary contacts and the terminal members are substantially filled with molded insulating

material supporting members

36 and 38, respectively. Each such member is provided with a

groove

36a, 38a around three sides thereof as shown in FIG. for accommodating the associated stationary contact and is rigidly secured to the associated terminal member by a pair of

screws

36b, 36c and 38b, 38c extending through the terminal member into threaded engagement in a pair of tapped holes in opposite corner portions thereof as shown in FIGS. 2 and 5.

Molded members '36 and 38 support are blowout magnets of the permanent magnet type for the respective sides of an arcing contact bridge hereinafter described. For this purpose, elongated

permanent magnets

40 and 42 are embedded or molded in

members

36 and 38, respectively, and extend transversely through the left-hand end portions of the latter slightly beyond the opposite sides thereof as shown in FIGS. 3, 5 and 9. A pair of non-magnetic pins 36d are molded in member '36 and a pair of pins 38d are molded in member 38 for supporting magnet pole pieces. The pins of each such pair are arranged parallel to the associated magnet above and below the latter and are longer than the associated magnet so that the ends thereof extend beyond the ends of the magnet. A pair of gene-rally rectangular

flat pole pieces

40a and 40b shown in 5 and each having a pair of holes therein are thereby assembled on the opposite ends of pins 36d to engage the flat opposite ends of magnet 40.

Similar pole pieces

42a and 42b shown in FIGS. 7, 8 and 9 are assembled on pins 38d to engage the ends of magnet 42. The pairs of pole pieces may be held in place by magnetic attraction but the opposite ends of the pairs of pins 36d and 38d may also be riveted over the pairs of pole pieces as shown in FIG. 9 to rigidly secure the same in place. As shown in FIGS. 2 and 7, the pairs of

pole pieces

40a, 40b and 42a, 42b extend on opposite sides of and beyond the respective arcing contacts to form magnetic air gaps across the latter to blow the electrical arcs when the contacts are opened into arc extinguishing horns hereinafter described.

As shown in FIGS. 3 and 4, a flat plate 44of insulating material is rigidly secured to the outer surface of armature 8, plate 44 having a narrower upper end portion 44a extending beyond the upper end of the armature. An insulating sheet 46 having a configuration similar to that of plate 44 is interposed between plate 44 and armature 8 for purposes hereinafter described. Stud 8e extends through holes 46a and 44b shown in FIG. 4 and is provided with suitable washers 48 and a nut 50 rigidly to secure plate 44 and sheet 46 to armature 8. A spring pin 8 extends from a hole in armature 8 through a hole in sheet 46 and partway into a hole in plate 441.20 p'revent rotation thereof on stud 8e. portion 44a of plate 44 is provided with a recess 446 to reduce the thickness thereof for accommodating an elongated movable current carrying contact bridge 52, the edge of contact bridge 52 being confined against shoulder 44d to maintain the contact bridge transversely on plate 44. The end surfaces on one face of contact bridge 52 are provided with contacting members 52a comprising a metal having good electrical conducting characteristics such as silver or the like for engaging contacting members Me and 26e of the stationary contacts to bridge the latter when the electromagnet is'energized. As shown in FIGS. 4 and 6, an enlarged head pin 54 extends through a. hole in the narrow portion 44a of plate 44 and a hole in the midportion of contact bridge 52. A helical compression spring 56 surrounds pin 54 and is stopped against a washer 54a surrounding pin 54 and a slotted-end adjusting nut 54b threaded on the pin, there beinga retaining pin 54c extending through pin 54 intermediate the ends thereof and through the slots to restrain the nut from rotating. Spring 56 resiliently presses contact 52 against plate 44 in the recess thereof. The holein portion 44a of plate 44 is provided with a counterbore 44h to accommodate the head of pin 54 and insulating sheet 46 overlies the head of pin'54 to insulate the latter from the upper end of armature 8.

As shown in FIGS. 3 and 4, an arcing contact plate or bridge 58 overlies current carrying contact bridge 52 and The narrow end;

is resiliently secured to insulating plate 44. Contact plate 58 is provided with a large hole 58afreely to clear nut 50. Contact plate 58 is provided with a hole 58b adjacent the lower end thereofand another hole 580 adjacent one side thereof for freely receiving pins 441: and 44 respectively, to hold contact plate 58 in registration with its supporting insulating plate 44, pins44e and 44f being rigidly secured to insulating plate 44. A short bushing 44g surrounds pin 44 to space the lower end of contact plate 58 from insulating plate 44 thereby to aiford rocking of the movable arcing contacting members on the stationary contacting members when the armature is actuated and to attain large surface area engagement between the movable'and stationary contacting members when the armature is in its attracted position.

As shown in FIG. 4, arcing contact plate 58 is generally U-shaped orbifurcated at its upper end and the end surfaces of one face of the bifurcated portions have secured thereto contacting members 58d of metal having good electrical conductivity such as silver or the like for engagement with contacting members 240- and 260 to bridge the stationary contacts when the armature is attracted. The midportion of contact plate 58 directly below the slot between the bifurcated portions is provided with a hole 582 for freely accommodating'pin 54 and spring 56 surrounding the latter. Hole 58:; is provided with a vcounterbore 58f for accommodating one end of i a helical compression spring 66 surrounding pin 54 and spring 56. The other end of spring 60 is stopped against a steppedwasher 54d surrounding pin 54 and a slottedendadjusting nut 54e threaded on the end of the pin, there being aretaining pin 54f extending through pin 54 and throughthe slots in the nut as shown in FIG. 6 to re-.

strain the nut from turning. Spring 60 resiliently presses contactplate 58 against contact bridge 52 as shown in As shown in FIGS. and 9, each molded member, such as

members

36 and 38, is provided at its upper and lefthand end portions on opposite sides thereofwith

grooves

36a, 38a forming a stepped portion for receiving. the

complementary portion of each

arc shield

62, 64 shown in FIGS], 9 and 11. Each

arc shield

62 and 64 is formed of two

complementary portions

62a and 62b, 64a and 64b of insulating material secured to one another by a plurality of

bolts

62c and 64c,.respectively, to form an.

enclosure. closed at the top and partially closed at the bottom and havingopen ends. One complementary portion 64raof arc shield 64 is shown in FIGS. 10 and 11.

Portion64a is provided with a wall 64d along the upper portion thereof for engagement with a complementary wall on the other portion as shown in FIGS. 1 and 9. A relatively shorter lower wall 642 is provided as shown in FIGS. 10 and 11 for engagement witha complementary lower wall on the other portion as shown in FIG. 1. The aforementitoned bolts 64c extend-through these upper and lowerwalls to clamp the two side portions together. A groove 64 is provided along the right-hand portion shown in FIG. 11 to provide a reduced portion for receipt in groove 38:: in molded member 38 as shown inEIG. 9 to providethe arc shield with close-fitting engagementaround the stationary contacts. As shown in FIGJ'I9, the arc shield 64 fits over molded member 38 betweenpthelatter and the'associated pole pieces 42a and 4212 so that the pole pieces extend. externally of and A clamping bar 66 having a clamping bolt 68 extend ing therethrough and through mounting panel 2 is providedfor clamping the arc shields in place, bolt 68 exte'ndingthrough the space between the innermost opposed pole pieces 40b and 420 as shown in FIG. 1. Each arc shield is provided with a

recess

62h, 64h for accomby the curved upper surface of the upper leg 24a, 26a of I each stationary contact. One end of arc horn member 70 is adjacent stationary contact 26 as shown in FIG. 3 and the other end extends externally of the associated arc shield 64 and is providedwith an electrical connector such as a bolt 70a or the like. The end of arc horn member 7li-adjacent stationary contact 26 is spacedfrom the stationary contact a shorter distance than the distance between contact members 260 and 58d when the contacts" are open as shown in FIG. 3 to improve the transfer of the are from the contacts to the arc horn when the contacts are-opened.

An electrical conductor 72 shown in FIG. 1 connects the external ends of arc horn members 70 to one another and another electrical conductor 74 connects the external end of one arc horn member 70'to bridging contact mem! ber 58 as most clearly shown in FIGS. 3 and 4. In this manner, arc horn members 70 are maintained at the same electrical potential as bridging contact member 58.

A pair of bolts 76 are rigidly secured to mounting panel 2 and extend past the opposite sides of armature 8 and the bridging. contact assembly. A stopping bar 78 is coi1-- nected across the ends of these bolts to form a stop for the opening movement of the bridging contacts when the electromagnet is deenergized. As shown in FIG. 3, one of the bolts 76 lies between coil terminals 4a and 4b to prevent the coil from rotating. The bolts 76 are covered by insulating sleeves 76a to insulate the bolt from the coil terminals As shown in FIGS. 2 and 3, mounting panel 2 is provided with counter-bores on the rear face thereof to ac' commodate the ends of the bolts and threaded inserts which are secured thereto. An insulating sheet 80 overliesthese counter-sunk bolt ends except bolt 68 to insulate: the same from one another and from the connector port1ons 28b and 30b of terminal members 28 and 30. The lefthand end of bolt 68, as shown in FIG. 2, is provided with a removable thumb screw 68a threaded intoan axial tapped hole in the end of a hexagonal portion 68b of the The rightbolt to facilitate removal of the arc shields. hand end of bolt 68 is provided with an annulargroove' for accommodating a retaining ring .680, there being a washer 68d betweenretaining ring 68c and the bottom of the recess or counter-bore in panel 2 The right-hand end Y of bolt 68 is threaded and extends beyondpanelz provid-q ing means for securing the contactor assembly to amounting structure or the like. The portion of bolt 68 immediately adjacent the front surface of panel 2 is hexagonal in shape so that it can be gripped by a wrench and turned into a threaded hole in the mounting structure. 7

As shownin FIGS. 10 and 11, each half portion of each of thetwo arc shields such as half portion 64a of arc" shield 64 is provided with an angularinternal wall 64g. The other half portion of each arc shield such as portion 64b is provided with a complementary angular wall 64g shown in FIGS. 7 and 8. These two

walls

64g and 64g engage one another along their inwardly projecting edges completely to close the interior of the arc shield enclosure" throughout the length of these walls. These walls in'each arc shield surround the end and the b ack of each leg of arcing contact bridge 58 as shown in FIG.3. These walls prevent the are from flashing between the rear side of the leg of the arcing contact bridgeand the rear side of the V arc horn member 70 thereby to enhance the transfer of i the arc to the arc horn when the arcing contacts are i opened. I v v Each half portion of each arc shield is provided with an elongated cavity such as cavity 64k shown in FIGS. 3, I 7; .10 and 11. As shown in FIGS. 3 and 7, these cavities j are in registration with one another and extend along the inner surfaces of the arc shield in the area in registration with the space between the arcing contacting member and the associated stationary contact. More specifically, cavity 64k as shown in FIG. 3 extends in registration with the surface of stationary contact member 26c from the lower end thereof between stationary contact 26 and are horn member 70 slightly beyond the end of arc horn member 70. The purpose of these cavities 64k is to afford insulating surfaces perpendicular to the direction of the arc. Melted contact material is not likely tobe deposited on these perpendicular surfaces and, therefore, these cavities prevent establishment of deposited material conducting paths between the stationary contact and the arcing contact bridge and between the stationary contact and are horn member 7 0.

. As shown in FIGS. 3, 7, 8 and 11, groove 64 for are horn member 70 is provided with a stepped upper wall to provide a narrow slot 641 extending along are born member 70. This slot is small enough so that the are traveling along the horn does not enter therein. This slot is also large enough so that deposited contact material or are horn material will not bridge the space between arc horn member 70 and the insulating interior wall of the arc shield. Such bridging of the arc horn member by deposited material on the interior walls of the arc shield might cause the arc to hang up and cause burning of the arc shield. Slot 641 prevents such burning of the arc shield. a i

. As shown in FIGS. 7 and 9, a narrow slot 64m is provided between the opposite sides of each stationary contact such as contact 26 and the adjacent interior walls of the arc shield. These slots 64m extend throughout the portions of the arc shields where such portions are adjacent the stationary contacts. The size of these slots 64m and their purpose are similar to that described in connection with slots 641 along arc horn member 70. When operating coil 4 is energized, armature 8 is attracted to the end of core 6 having washer 6a secured thereto. Armature 8 pivots on edge 8a thereof in the clockwise direction to cause compression of return springs 22. The magnetic attraction of armature 8 maintains pivot 8a thereof against bar 16, Arm 8d actuates switchZO.

Armature 8 carries the assembly" comprising insulatingsheet 46, insulating member 44, current carrying contact bridge 52 and arcing contact plate 58. As armature 8 pivots in the clockwise direction, FIGS. 2, 3 and 6, contacting members 580? of arcing contact plate 58 first engage contactingmembers 24c and 260 of

stationary contacts

24 and 26, respectively, to bridge the stationary contacts. As the armature pivots further, current carrying contact bridge 52 separates from arcing contact plate 58 and spring 60 is compressed. Spring 56, however, maintains current carrying contact bridge 52 in engagement with insulating plate 44 to move with the latter. Itwill be apparent that during such further pivoting of the armature, arcing contact plate 58 pivots on pin 44] relative to insulating plate 44 and that the pivot point, that is, pin 44 of arcing contact plate 58 moves toward the right in FIG. 3. This imparts a rocking movement to contacting members 58a to rock the same into'large area surface engagement with stationary contacting members 240 and 260. Thereafter, contacting members 52a of current carrying contactbridge '52 engage stationary contacting members Me and 26e to bridge the stationary contacts. Further pivoting of the armature into engagement with washer Go on the end of core 6 causes spring 56 to be compressed as current carrying'contact bridge 52 separates from insulating plate 44. Such separation of contact bridge 52 and plate 44 allows contacting members 52a to settle into, large area surface engagement with stationary contacting

members

24c and 26e. Also, spring 56 maintains sufiicient contact pressure thei'ebetween to establish a good electrical connection. When spring 56 is compressed as aforestated, spring 60 is compressed further:

contacts and into the arc horns.

to maintain suflicient contact pressure between the arcing contacting members. I

When coil 4 is deenergized, return springs 22 pivot armature 8 in the counterclockwise direction to open the contacts and to interrupt the electrical connection therethrough at two points in series. When armature 8 starts to pivot, insulating plate 44 engages current carrying contact bridge 52 to move the latter in the left-hand direction in FIG. 3 and to disengage contact members 52a from stationary contacting members Me and 26e to interrupt the current carrying connection. As armature 8 starts to pivot as aforesaid, spring 56 maintains the current carrying contacts closed while the gap between insulating plate 44 and contact bridge 52 closes. Insulating plate 44 first engages contact bridge 52 at the upper portion thereof as seen in FIG. 3. to impart to contact bridge 52 a counterclockwise rocking movement. This tends to break any weld between the current carrying contacting members. As the armature pivots further following opening of the current carrying contacts, spring 60 maintains the arcing contacting members closed as the gap between contact bridge 52 and contact plate 58 closes. This pivoting of the armature also causes pivot pin 44f'to move in the left-hand direction in FIG. 3 thereby to impart a clockwise rocking movement to the arcing contacting members 53d. This tends to break any weld between the movable and stationary contacting members. After contact bridge 52 engages contact plate 58, the arcing contacting members open in response to the complete pivoting of the armature in the openingdirection. During the clockwise and counterclockwise pivoting of the armature, springs 22 apply a force on the end of arm 8b in a direction tending to maintain pivotal edge 8a of the armature in its seat against bar 16.

Permanent magnets

48 and 42 are polarized in opposite directions so that the arcs between the respective stationary contacts and the legs of arcing contact plate .58 are blown in a direction away from the current carrying As the arcing contacting members 580! separate from the stationary contacts, the arcs drawn therebetween are blown upwardly in FIGS. 1, 2 and 3 by the magnetic fields produced by the

permanent magnets

40 and 42 between the pole pieces of the respective pairs thereof. The direction in which the arcs are moved is expressed by Flemings left-hand rule. According to this rule, if the forefinger is pointed in the direction of the flux between the pole pieces and the middle finger is pointed inthe direction of the current in the arc, the thumb will point in the direction in which the arc will move.- Assuming that in FIG. 3, the current flows downward in terminal 30 and in the lefthand direction in the lower leg 26b of the stationary contact and across the gap into arcing contacting member 58d and out through the other terminal, then permanent magnet 42 must have a polarity of a north pole at its left end and a south pole at its right end as viewed in' FIG. 1 or a south pole at its near end and a north pole at its far end in FIG. 3. This polarity will cause the magnetic flux which passes from north pole piece 42a transversely of the arcing contact gap to south pole piece 42b to move the arc upwardly. As the arc moves upwardly, wall 64g in the arc shield prevents the are from striking between arcing contact plate 58 and are horn member '70. As shown in FIG. 3, the right-hand end of arc horn member 70 is nearer stationary contact 26 than is arcing contacting member 58d when fully open. This difference in distance between arc horn member 70 and stationary contact 26 relative to the distance between 'contacting members 58d and 260 enhances transfer-of the arc to the arc horn. The arc then moves outwardly along the upper surface of arc horn member 70 and the upper surface of stationary contact 26 until it ruptures and is extinguished. Upper legs 24a and 26a of

stationary contacts

24 and 26, respectively, are shorter than the lower legs 24b and 26b to provide an insulating air gap between such upper legs and the respectively associated terminal members 28 and'30. This air gap tends to prevent the arcs from running onto the terminal members.

The terminal membersare arrangedand constructed so that the currentsfiowing therein increase the magnetic force of the blowout magnets rather than decrease it. For example, current flowing downwardly in terminal member30 in FIG. 3 develops magnetic lines of force passing in the clockwise direction aroundthe terminal member when viewed. from above according to the Arnperefruleu As permanent magnet 42 is polarized with a south pole at its near end a north at its far end in FIG. '5 and the magnetic lines of force in a permanent magnet pass therethrough from the south end toward the north end, it will be apparent that the lines'of force developed by the current in the terminal members, are in the same direction and, therefore, tend to increase the blowout effect.

As will be apparent, conductor 72 electrically connects arc horn members 70 to maintain them at the same potential. Also, conductor 74 connects arc horn members 70 to arcing contact plate 58 to maintain them at the same potential thereby to facilitate transfer of the arcs from the arcing contacts to the arc horns under the action of the blowout. devices. Movable current carrying contact 52. is maintained in electrical connection with.

movable arcing contact plate 58 through springs 56 and 6.0 and bolt .54.

.As will be apparenhuse of the arcing contacts which close first and open last prevents arc damage to the current carrying, contacts. The bridging contact construction enables the contactor to control larger currents and voltages. This is for, the reason that'the electrical connection is interrupted in two places simultaneously. As the circuit is'interrupted in twoplaces, the voltage across the opening contacts on each side'of the bridging contact will be only one-half of what it would be across a single interrupting contact.

The terminal members 300 are widely spaced from other metallic members of the contactor to insulate the same from one another. The are shields62 and 64 are readily removable by removing thumb screw 68a andv clamping member 66 and conductor 74. Among other things, the

stationary contacts

24 and 26 are readily removablefr'om the front as seen in F16 1 without re- 7 moving the contactor base 2 from its mounting structure to which it may be secured by the threaded end of bolt 68. To remove stationary contact26, it is only necessary to remove screws 39d and 30a which are accessible from the front.- This permits removal of the assembly comprising terminal member 30, contact 26, molded member 38,'rnag net 42 andpole pieces 4 2 aand 4213. This facili tates replacement of the stationary contacts" 24 and 26.

The threaded nuts 54b and Sqte on bolt 54 afford easy adjustment of the forces of

springs

56 and 60. These nuts are provided with suitable slots to accommodate locking pins 540 and 54 to lock the nuts in adjusted positions. Use of alnico permanent magnets and 42 atfords strong magnetic fields for extinguishing the arcs. Cavity 64k prevents deposited contact material-from establishing an electrical path between the contacts or between ing contact bridge for engaging said stationary contacts to complete an electrical connection therethrough a movable supporting member, and means mounting said arcing contact bridge and said current carrying contact bridge on said supporting member, and resiliently biasing themindependently against one side of said supporting member in stacked relation for successive separation from the latter as said contact bridges close against said stationary contacts whereby said arcing contact bridge closes the connection first and opens the connection last and said current carrying contact bridge closes. the connection last and, opens the connection first across said stationary contacts when said supporting member is moved inopposite directions, and said contact bridges each cause interruption of the connection between said stationary contacts in two places thereby to afford interruption of higher voltage converging ends a distance less than the distance between,

the arcing contact bridge and the associated stationary contact in their open condition. a

5. The invention defined in claim 1, wherein each said stationary contact is provided with a first portion for engagement by said arcing contact bridge and a second portionufor engagement by said current carrying contact bridge, and the distance between said first portion and said arcing contact bridge is less than the distance be-. tween said second portion and said current carrying con-1 tact bridge when said contact bridges are disengaged from said stationary contacts.

6. The invention defined in claim 1, together with an arc shield for each side of said arcing contact bridge, each said are shield comprising an enclosure of insulating material surrounding and covering the associated stationary contact and the portion of said arcing contact bridge which engages the latter, and an electrically conducting member mounted Within each said enclosure forming with the associated stationary contact an arc horn diverging from near the point of engagement between saidarcing contact bridge and the associated stationary contact.

7. The invention defined in claim 6, wherein each said are shield enclosure comprises a closedinternal Wall between and separating said electrically conducting arc horn member from said arcing contact bridge to prevent an electrical are from being established between said are born the portions of the arc horn. And slots MI and 64m tend to prevent the arcs from burning the arc shields.

While the apparatus and structures hereinbefore described are effectively adapted to fulfill the objects stated,

it is to be understood that I do not intend to confine my invention to the particular preferred embodiment of elec- 'tric switch having arc extinguishing means disclosed,

inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

I claim: 1. In an electric switch, two stationary contacts mounted in spaced apart relation, a movable arcing contact bridge for engaging said stationary'contacts to complete an electrical connection therethrough, a movable current carrymember and the rear surface of said arcing contact bridge.

8. The invention defined in claim 6, together With a pair of cavities in the opposed internal walls of said are shield enclosure on opposite sides of the gap between said arcing contact and immediately adjacent said stationary contact bridge and the associated stationary contact, and each said cavity having walls extending perpendicular to the direction of movement of said arcing contact bridge to prevent deposited contact material on the interior of said enclosure from establishing an electrical path between said arcing contact bridge and the associated stationary contact.

9. In an electric switch, two stationary contacts mounted in spaced apart relation, a movable arcing contact bridge for engaging said stationary contacts to complete an electrical connection therethrough, a movable current carrying contact bridge for engaging said stationary contacts to complete an electrical connection therethrough, a movable supporting member, and means mounting said arcing contactbridge and said current carrying cona ll ing contact bridge closes the connection first and opens the connection last and said current carrying contact bridge closes the connection last and opens the connection first across said stationary contacts when said supporting member is moved in opposite directions, and said contact bridges each cause interruption of the connection between said stationary contacts in two places thereby to afford interruption of higher voltage connections, an arc shield for each side of said arcing contact bridge, each said are shield comprising an enclosure of insulating material surrounding and covering the associated stationary contact and the portion of said arcing contact bridge which engages the latter, and an electrically conducting member mounted within each said enclosure forming with the associated stationary contact an arc horn diverging from near the point of engagement between said arcing contact bridge and the associated stationary contact, said electrically conducting arc horn member comprising an elongated flat strip having one end adjacent the associated stationary contact and the other end thereof extending away from said stationary contact, and opposed grooves in the interior walls of said arc shield enclosure for retaining said strip, and each said groove being provided with a wall spaced from the arc-running surface of said fiat strip to provide a slot therealong small enough to prevent the are from entering therein and being effective to prevent the are from burning the insulated wall of said enclosure.

10. In an electric switch, two stationary contacts mounted in spaced apart relation, a movable arcing contact bridge for engaging said stationary contacts to complete an electrical connection therethroug'h, a movable current carrying contact bridge for engaging said stationary contacts tocornplete an electrical connection therethrough, a movable supporting member, and means mounting said arcing contact bridge and said current carrying contact bridge on said supporting member whereby said arcing contact bridge closes the connection first and opens the connection last and said current carrying contact bridge closes the connection last and opens the connection first across said stationary contacts when said supporting member is moved in opposite directions, and said contact bridges each cause interruption of the connection between said stationary contacts in two places thereby to afford interruption of higher voltage connections, an arc shield for each side of said arcing contact bridge, each said are shield comprising an enclosure of insulating material surrounding and covering the associated stationary contact and the portion of said arcing contact bridge which engages the latter, and an electrically conducting member mounted within each said enclosure forming with the associated stationary contact an arc horn diverging from near the point of engagement between said arcing contact bridge and the associated stationary contact; each said stationary contact being provided with a curved surface extending from the point of engagement by said 55 arcing contact bridge and forming with said electrically conducting member a diverging arc horn, and the interior walls of said are shield enclosure being spaced from opposite edges of the curved surface of said stationary contact to provide slots therealong small enough to prevent the are from entering therein and being efiective to prevent the are from burning the insulated walls of said enclosure.

-11. In an electric switch, two stationary contacts mounted in spaced apart relation, a movable arcing contact bridge for engaging first portions of said stationary contacts to complete a first electrical connection theret-hrough, a movable current carrying contact bridge for engaging second portions of said stationary contacts to complete a second electrical connection therethrough in parallel with said first electrical connection, a pivotal supporting member, means mounting said contact bridges on said supporting member to eifect engagement between spaced portions of said arcing contact bridge and said first portions of said stationary contacts when said supporting member is pivoted in one direction and to effect engagement between spaced portions of said current carrying contact bridge and said second portions of said stationary contacts when said supporting member is pivoted further in said one direction, and said mounting means comprising means efiective when said supporting member is thereafter pivoted in the opposite direction to cause separation of said current carrying contact bridge from said second portions of said stationary contacts first and thereafter to cause separation of said arcing contact bridge from said first portions of said stationary contacts, and

said arcing contact bridge causing interruption of the electrical'connection between said stationary contacts at two points in series thereby to afford interruption of a higher voltage connection, said mounting means comprising resilient means biasing said current carrying contact bridge and said arcing contact bridge independently of one another, in overlapped relation in that order against said supporting member, said resilient means allowing separation of said arcing contact bridge from said current carrying contact bridge following engagement between said arcing contact bridge and said stationary contacts and allowing separation of said current carrying contact bridge from said supporting member following engagement between said current carrying contact bridge and said stationary contacts when said supporting member is pivoted in said one direction. 5

References Cited in the file of this patent UNITED STATES PATENTS 529,213 Sweet Nov. 13, 1894 1,901,573 Wilms Mar. 14, 1933 2,427,074 Scott Sept. 9, 1947 2,945,109 Fehling July 12, 1960 3,031,552 Stewart Apr. 24, 1962 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 132,225 May 5', 1964 Merle R. Swinehart Column 10, lines 59 and 60, for "arcing contact and immediately adjacent said stationary contact bridge and the associated stationary contact," read arcing contact bridge and the associated stationary contact and immediately adjacent said stationary contact,

Signed and sealed this 15th day of September 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER smsting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3, 132,225 1 May 5-, 1964 Merle R, Swinehart Column 10, lines 59 and 60, for "arcing contact and immediately ad acent said stationary contact bridge and vthe associated stationary contact," read arcing contact bridge and the associated stationary contact and immediately adjacent said stationary contact,

Signed and sealed this 15th day of September 1964.

(SEAL) Attcst:

ERNEST SWIDER EDWARD J. BRENNER Aittc's ting Officer Commissioner of Patents

Claims

1. IN AN ELECTRIC SWITCH, TWO STATIONARY CONTACTS MOUNTED IN SPACED APART RELATION, A MOVABLE ARCING CONTACT BRIDGE FOR ENGAGING SAID STATIONARY CONTACTS TO COMPLETE AN ELECTRICAL CONNECTION THERETHROUGH, A MOVABLE CURRENT CARRYING CONTACT BRIDGE FOR ENGAGING SAID STATIONARY CONTACTS TO COMPLETE AN ELECTRICAL CONNECTION THERETHROUGH, A MOVABLE SUPPORTING MEMBER, AND MEANS MOUNTING SAID ARCING CONTACT BRIDGE AND SAID CURRENT CARRYING CONTACT BRIDGE ON SAID SUPPORTING MEMBER, AND RESILIENTLY BIASING THEM INDEPENDENTLY AGAINST ONE SIDE OF SAID SUPPORTING MEMBER IN STACKED RELATION FOR SUCCESSIVE SEPARATION FROM THE LATTER AS SAID CONTACT BRIDGE CLOSE AGAINST SAID STATIONARY CONTACTS WHEREBY SAID ARCING CONTACT BRIDGE CLOSES THE CONNECTION FIRST AND OPENS THE CONNECTION LAST AND SAID CURRENT CARRYING CONTACT BRIDGE CLOSES THE CONNECTION LAST AND OPENS THE CONNECTION FIRST ACROSS SAID STATIONARY CONTACTS WHEN SAID SUPPORTING MEMBER IS MOVED IN OPPOSITE DIRECTIONS, AND SAID CONTACT BRIDGES EACH CAUSE INTERRUPTION OF THE CONNECTION BETWEEN SAID STATIONARY CONTACTS IN TWO PLACES THEREBY TO AFFORD INTERRUPTION OF HIGHER VOLTAGE CONNECTIONS.