GB2150761A - Electrical contactor - Google Patents

Abstract

An electric contactor, e.g. of the vacuum type, comprises a unitary member (38) formed (preferably molded) from insulating material and including a pair of generally cruciform trunnion portions (90) on opposite ends thereof, each trunnion portion being disposed and firmly engaged in an annular bearing member, e.g. the inner race of a ball or roller bearing (48), which is rotatably supported in a frame (14). The spaces (104) between the cross- arms of each cruciform trunnion portion (90) preferably are filled with a resin, e.g. epoxy. <IMAGE>

Description

SPECIFICATION Electrical contactor with improved crossbar structure This invention relates generally to electrical contactors and, more particularly, to a cross-bar and bearing arrangementtherefor.

As well known in the art, contactors, said to be ofthe air-breaktype orthevacuum type according as their contacts operate in air or in an evacuated envelope or so-called vacuum bottle, are widely employed forthe purpose of performing switching operations, such as the starting and stopping of motors, for example.

Vacuum type contactors, such as the one illustrated in Applicant's Descriptive Bulletin ILl 6-200-32 "Westinghouse Type SJAVacuum Contactor" published in 1982,offercertain advantages over air-breaktype contactors ofcomparablevoltage ratings, one of which is considerably less bulk due to the factthatthe contacts of a vacuum type contactor operate in a vacuum, thus requiring smaller clearances and less contact separation so that the mechanisms for operating the contacts likewise can be smaller and more compact.This compactness of vacuum-type contactors, regarded by manufacturers as well as users as a distinct advantage, also poses a challenge to designers insofar as the crowding together of component parts within the small space available can create dielectric interference and breakdown problems, especially when the component parts include metallic elements extending proximate to and between points of different potentials.One such element two be found in conventional vacuum type contactors such as, for example, the one shown intheabove-mentioned Descriptive Bulletin, is a metallic shaft used to support what is generally referred to in the art as the cross-bar assembly, i.e. the movable structure which translates the action ofthe contact operating means, such as an electromagnet and kickout springs, into movements ofthe contacts and is common to, thus extending across, all phases of the contactor.

The invention has for its principal object to alleviate these problems, and it resides accordingly in an electriccontactorincluding a frame, contact means movable to contact-open and contact-closed positions, operating means including a movable structure which is operatively connected to the contact means and pivotally movable so as to open and close same, and a pair of bearing assemblies pivotally supporting the movablestructurefrom said frame; said movable structure comprising a unitary member formed of an electrical insulating material and including two substantially cruciform trunnion portions disposed on opposite ends thereof, each of said bearing assemblies including an annular bearing memberwhich is rotatably supported in said frame and has one of said substantially cruciform trunnion portions ofthe unitary memberfirmly inserted therein.

This arrangement employing a unitary member formed of insulating material and including cruciform trunnion portions with annular bearing members thereon provides strong pivotal supportforthe movable structure withoutthe use of a metallic shaft orthe like. The unitary membertogetherwith its cruciform trunnion portions lends itself well to molding, and the trunnion portions, being cruciform, can be readily held within close tolerances enabling them to be accurately fit into the annular bearing members with relative ease.Preferably, the spaces defined between adjacent cross-arm portions bythecross- arms of each cruciform trunnion portion and the annual bearing memberthereon arefilledwith a cast resin, such as epoxy, so as to round out each trunnion portion and thus increase its strength.

In a preferred embodiment ofthe invention to be described in detail hereinafter, the annular bearing members on the trunnion portions ofthe unitary member are the inner races of ball or roller bearings which, latter are disposed in generally U-shaped recesses formed in insulating portions ofthe contactorframe, and which are retained in said recesses by means of resilient members each secured to the frame in bridging relationship with respect to the open end ofthe associated U-shaped recess and engaging the outer periphery ofthe bearing seated therein. This arrangement both facilitates the installation ofthe movable structue in the contactorframe, and permits the two bearing assemblies of the movable structure to self-align with one another.

The preferred embodiment of the invention will now be described, byway of example only, with reference to the accompanying drawings, in which: Figure lisa front elevational view of a three-phase, alternating-current vacuum-type contactor embodying the invention; Figure 2 is a side elevational, partly sectional view of the contactor, with some parts broken away for clarity; Figure 3 is a rear elevational view ofthe contactor; Figure 4 is a front elevational view of the movable structure ofthe contactor; and Figure 5 is a side elevational and partly sectional view ofthe movable structure.

Referring nowto the drawings, and to Figs. 1 to 3 in particular, the three-phase alternating-current vacuum contactor 10 shown therein includes a preferably metallic mounting plate orframe 12 to which is secured, e.g. bolted as at 16, a frame 14formed of a suitable insulation, such as plastics material. Relative sliding motion between the frame 12 and frame 14 is further prevented by means of a dowel or index ring member 18 on the frame 14 disposed in a complementary hole or opening 20 in frame 12. Three vacuum switches 22 are provided, one for each ofthe three phases ofthe electrical system which the contactor 10 controls. Each switch 22 has associated therewith a pair of terminals 26 and 28, the latter of which is electrically connected to a movable contact stem 30 through aflexible conductor 32. The movable contct stem 30 has disposed thereon a spring-loaded flange member 34 and a threadedly engaged flange member o r cognut 36, between which extends a portion 40 of an electrically insulating cross-bar member38, the portion 40 having fastened thereto, as at 43 (Fig. 5), a pivot plate 42 pivotally engaging the aforementioned flange member 36. The cross-bar member38 has an arm portion 44 and it includes a pair of coupling posts 46 extending therefrom, and two bearing assemblies 48 disposed on the opposite ends ofthe cross-bar member 38 and seated in U-shaped recesses 49 formed in the insulating frame 14.

Mounted on the arm portion 44 is a magnetic armature 52 having associated therewith an electromagnet 54 which is disposed on the frame 12. Connected to the frame 12 is one end of a spring 56 having its other end connected to a link bar 58 which is loosely, i.e.

releasably, coupled with the posts 46. When the electromagnet 54 is in a deenergized state, the spring 56 holds the link bar 58 in a position adjacent the upper ends 60 of openings 84formed in the frame 12, thus holding the cross-bar member 38 in the clockwise position shown in Fig. 2 and in which position the movable contact means 30 ofthe vacuum switches 22 are in their lowered, e.g. contact-open, positions.

Upon energization ofthe electromagnet 54, the armature 52 is attracted, thus causing the cross-bar member 38to be rotated, in its bearing assemblies 48, counter-clockwise againstthe action ofthe spring 56 so thatthe cross-bar portions 40, in cooperation with the spring-loaded flanges 38 on the associated contact stems 30, will lift the latter to their actuated, e.g.

contact-closed, positions. As mentioned hereinbefore, the cross-bar member 38 is pivotally supported in the insulating frame 14 by means of the bearing assemblies 48 seated in the respective U-shaped recesses 49. Each bearing assembly 48 is held in the associated recess 49 by means of a flexible member53 secured, adjacent opposite ends thereof, to portions ofthe frame 14 by means of screws or bolts 55, and bridging the opening of the recess 49 so as to retain the bearing assembly 48 in place, the arrangement being such asto provideforself-alignmentofthe bearing assemblies 38 within the frame 14.

Referring once more to Figs. 2 and 3, the spring 56 is connected to the frame 12 through spring adjusting means. More specifically, the frame 12 comprises two lateral flange portions 62 and a backplate 61 therebetween, the latter having secured, e.g. bolted, thereto, as at 68 (Fig. 2) the electromagnet 54 and having thereon a spring anchor 64 comprising a bracket secured to the back plate 61 by means of bolts, such as bolt70. Supported from bracket 64 are two slightly inwardly angled adjusting screws 72 which carry a retainer 73 th readedly engaged with the screws 72 and having a hook portion 74 of the spring 56 attached thereto. At its opposite end, the spring 56 has a hook portion 76 which is inserted in an opening 78 formed in the link-bar 58.The link-bar 58 has formed therein symmetrically disposed rectangular cutouts 80 in which indexed end portions ofthe coupling posts 46 of the cross-bar member 38 are engaged, and in which said end portions are held engaged through the action ofthe spring 56 pulling the link 58 against the posts 46, the latter extending through elongage openings 82 provided in the back plate 61. Movement of the link-bar 58 under the influence ofthe spring 56 is limited by the opposite end walls of the elongate openings 84 in the lateral flange portions 62A of the backplate 61.

Whilstthe electromagnet 54 is deenergized,the spring 56, acting through the link 58 and the coupling posts 46, maintains the cross-bar assembly 38 and the movable contact stems 30 ofthe vacuum switches 22 in the position shown in Fig. 2, which is assumed herein to be the contact-open position ofthe switches 22. When electrical power is supplied to the electro magnet54through terminals 86, the armature 52 is magnetically attracted and thereby causes the crossbar assembly 38 to be rotated counter-clockwise against the action of the spring 56, thus lifting the movable contact stems 30 of the vacuum switches 22 so as to close the contacts of the latter.

Whenever it is desired to service or replace internal parts of the contactor, e.g. the operating coil ofthe electromagnet 54, and therefore it becomes necessary to remove the frame 14fromtheframe 12, this can be done without disturbing the adjustment of the spring 56. It is achieved simply by releasing the screws 16 (Fig.2) and puliing theframe 14fromtheframe 12 far enough to withdraw the dowels 18 from the holes 20, thereby enabling the spring-loaded link 58 to become seated against the stops formed bythe end walls 60 of the elongate openings 84.This removes the spring tension from the coupling posts 46 and thus enables them to be readily withdrawn from the link 58 upon compiete removal ofthe frame 14 away from the frame 12. However, the spring assembly comprising the link 58 and the kickout spring 58 is left undisturbed and in a condition readyforsubsequent reconnection with the contactor mechanism without a need for readjustment of the spring 56.

As seen from Fig. 5, the movable structure comprising the cross-bar member 38 has the armature 52 (which is formed of magnetic plates 98) secured, e.g.

riveted as at 100, to the arm portion 44 of the cross-bar member, and has the pivot plates 42 (which pivotally engagethe cognuts 36 on the contact stems 30 ofthe various vacuum switches 22) secured, e.g. bolted as at 43, to the respective cross-bar portions 40. The cross-bar member 38 itself is a unitary member formed of a suitable insulating material, such as plastics, and including two substantially cruciform trunnion portions 90 formed at opposite ends thereof.

With particular reference to Fig. 2 illustrating one of the two bearing arrangements ofthe cross-bar member as representative of both, it is seen therefrom that the cruciform trunnion portion 90 shown therein is disposed within the rotatable, annular inner bearing member, or race, of a ball or roller bearing, being firmly inserted therein such thatthe distal ends ofthe cross-arms 93 and 94 (see also Fig. 5) of the cruciform trunnion portion, along their outer edges, such as edges 91 and 92, are in firm frictional engagement with inner peripheral surface portions of the inner race so thatthe cross-bar member and the inner bearing members on its cruciform trunnion portions will rotate as one.

Preferably, the spaces, such as space 104, defined by the inner bearing member and the cross-arms 93, 94 between adjacent cross-arm portions a refilled with a hardened cast resin, such as epoxy, thereby in effect to "round out" the cruciform trunnion portion 90 and thus add strength to the bearing.

It will be appreciated thatthe above arrangement embodying the invention provides strong and durable bearing supportforthe movable structure without the use of a metallic shaft or other metallic parts capable of creating dielectric breakdown problems. Moreover, thecross-barmember38togetherwith the cruciform trunnion portions 90 thereon lends itself well to molding, e.g. injection molding, as readilyseenfrom Fig. 5 wherein the dash-dot line 102 with the step 104 therein indicates where the two sections of a suitable mold could meet, and wherein the arrows A and B indicate the directions in which the two sections would be moved in ordertojoin and, afterthe molding operation, to separatethem. twill be noted that the cross-arms 93 and 94 of each cruciform trunnion portion 90 extend in and perpendicularto, respectively, a plane containing the line 102 and the axis of rotation of the movable structure; thus, the cruciform trunnion portions 90 molded integral with the crossbar member 38 will not interfere when the two mold sections are separated upon completion of a molding operation.

Claims (4)

1. An electric contactor including a frame, contact means movable to contact-open and contact-closed positions, operating means including a movable structure which is operatively connected to the contact means and pivotally movable so as to open and close same, and a pair of bearing assemblies pivotally supporting the movable structure from said frame; said movable structure comprising a unitary memberformed of an electrical insulating material and including two substantially cruciform trunnion portions disposed on opposite ends thereof, each of said bearing assemblies including an annular bearing memberwhich is rotatablysupported in saidframe and has one of said substantially cruciform trunnion portions ofthe unitary memberfirmly inserted therein.

2. Anelectriccontactoraccordingtoclaim 1, wherein said unitary member is a molded member having said cruciform trunnion portions molded integral therewith.

3. An electric contactor according to claim 1 or 2, wherein each trunnion portion has cross-arms defining spacestherebetween and having distal ends thereof engaged with inner peripheral surface portions ofthe associated bearing member, said spaces being filled with a hardened resin.

4. An electriccontactoraccording to claim 1,2 or 3, wherein each of said bearing assemblies comprises a bearing having a rotatable inner race which constitutes said annular bearing member, each bearing being disposed in one oftwo generally U-shaped recesses formed in insulating portions of said frame, and being retained in the associated recess by means of a resilient member which is secured to the frame in bridging relationship with respecttothe open end of the associated U-shaped recess and is in engagement with the outer periphery of the bearing disposed in said recess.