US3105132A - Guide means for supporting a contact cross-arm of a circuit breaker - Google Patents

Description

Sept. 24, 1963 'c. L. JENCKS 3,105,132 GUIDE MEANS FOR SUPPORTING A CONTACT CROSS-ARM OF A CIRCUIT BREAKER Original Filed Dec. 19, 1958 2 Sheets-Sheet 1 INVENTOR 2 CHARLES L.ds-cKs ATTORNEY Sept. 24, 1963 c. 1.. JENCKS 3,105,132 GUIDE MEANS FOR SUPPORTING A CONTACT CROSS-ARM OF A CIRCUIT BREAKER Original Filed Dec. 19, 1958 2 Sheets-Sheet 2 IN V EN TOR CHARLES L. JENCKS FIG.

ATTORNEY United States Patent 3,105,132 GUIDE MEANS FOR SUPPORTING A CONTAUT CRGSS-ARM ()F A CIRCUIT BREAKER (Iharles Louis .lencks, Avon, Conn, assignor to General Eiectric Company, a corporation of New York Original application Dec. 19, 1958, Ser. No. 781,766, now

Patent No. 3,046,371, dated July 24, 1962. Divided and this application Get. 10, 1960, Ser. No. 61,761

2 Claims. (Cl. 200-168) My invention relates to electric circuit breakers and particularly to electric circuit breakers of the multi-pole type including movable contacts for each pole operated by an overcenter spring-type operating mechanism, the whole being enclosed in a casing of molded insulating material and suitable for use in industrial and commercial applications. This application is a division of copending application Serial Number 781,766, filed December 19, 1958, now Patent No. 3,046,371, assigned to the same assignee as the present invention.

It is a general object of the present invention to provide an industrial type circuit breaker having the physical dimensions of one type of commonly used prior art circuit breaker, for example, a 125 volt, 50 ampere circuit breaker, with a 5,000 ampere interrupting rating, which breaker has the electrical current carrying and interrupting capacities of the next largest size circuit breaker, even though such next largest size has a voltage rating four to five times as great and a short circuit interrupting capacity at least double, such, for example, as 480 or 600 volt, 100 ampere circuit breaker having a 10,000 amperes interrupting rating.

The higher voltage rating of such breakers requires that the mechanism and the associated parts including the terminals and insulating parts be relatively compact and spaced at proper distances to provide the required increased oversurface electrical clearance. The increased short circuit interrupting capacity requires the use of refractory type contacts, which, in turn, requires relatively higher contact pressure in order to maintain necessary low contact resistance. This, in turn, requires the provision of an operating mechanism capable of exerting a contact pressure substantially in excess of the prior art type breakers. In addition, such circuit breakers must be pro vided with a construction which can be readily manufactured and assembled and sold at relatively low cost. All of these overlapping and seemingly imcompatible requirements must be met in order to provide a circuit breaker of such increased rating.

Accordingly, it is an object of the present invention to provide an electric circuit breaker including an operating mechanism capable of exerting relatively high contact pressures and occupying a space no greater than prior art breakers of substantially lower rating.

It is a further object of the invention to provide a circuit breaker mechanism adapted to operate a multipole circuit breaker in which the contact cross arm supporting a plurality of contact arms is pivotally supported in the casing by cooperating bearing means comprising the side plates of the operating mechanism and the molded portion of the insulating casing, without the necessity for separate bearing members mounted in the casing.

In accordance with the invention, an electric circuit breaker is provided including a molded insulating casing having a plurality of side-by-side chambers, one of which is adapted to support and receive an operating mechanism, and a common contact cross arm extending across the circuit breaker chambers. The contact cross arm is supported for rotation by cooperating upper and lower bearing surfaces carried by the mechanism side irames and by front and rear bearing surfaces provided by the insulating casing, whereby the contact cross arm See need only be inserted into a slot-like opening in the side plates of the circuit breaker mechanism and then inserted into the molded insulating case, the mechanism being anchored in the insulating casing and the contact cross arm thereafter being trapped in position.

Other objects and advantages of the invention will, in part, be pointed out and, in part, become obvious from the following detailed description and the scope of the invention will be pointed out particularly in the appended claims.

In the drawings,

FIGURE 1 is a top plan view of a multipole circuit breaker incorporating the invention, a portion of the casing being broken away;

FIGURE 2 is a side elevation view partially in section taken generally on the line 22 of FIGURE 1 and showing the primary current path through one pole of the circuit breaker;

FIGURE 3 is a side elevation view of the operating mechanism, partially in section;

FIGURE 4 is a side elevation view of the operating mechanism, the parts being shown in automatically opened or tripped condition;

FIGURE 5 is a fragmentary sectional view, on enlarged scale, showing the details of mounting of the mechanism side-frames in the insulating casing;

FIGURE 5A is a fragmentary view .of a portion of the mechanism-supporting side frames of the circuit breaker of FIGURE 1;

FIGURE 6 is a fragmentary elevation view of a portion of the mechanism of a modified form of the invention adapted for use in a single-pole circuit breaker.

In the drawings, the invention is shown in FIGURE 1 as incorporated in a three-pole electric circuit breaker comprising an insulating casing including an insulating base portion 10 and an insulating cover portion 11. The base portion 10 includes three elongated side-by-side recesses 12, only one shown, each having a relatively stationary contact 13 mounted therein on a terminal strap 14 which, in turn, is connected to a line terminal 15, positioned in a recess located at one end of the circuit breaker. A relatively movable contact 16 is also provided in each of the chambers 12 and is carried by a two-part contact arm comprising a contact-carrying portion 17 and a mounting portion 18 which are pivotally interconnected by pivot pin 19. The contact-carrying portion 17 is biased for rotation about the pivot pin 19 with respect to the mounting portion 18 by means of a compresion spring 29, and such rotation is limited in the clockwise direction by the engagement of the contactcarrying portion 17 with an upwardly bent stop portion 21 carried by the mounting portion 13.

For the purpose of assisting in extinguishing arcs, each chamber 12 is provided with a series of spaced notched plates 13a, and a generally V-shaped grid 1311, through which are gases are forced to pass in escaping. The grids 13b are formed of relatively thick sheet metal having a plurality of closed spaced holes therein.

The mounting portion 18 of the contact arm is generally U-shaped and has aligned generally square openings in the opposite sides thereof adjacent the bight, through which a common contact cross arm 22 extends, having an enlarged hub portion of generally square cross section and a metallic reinforcing core 23. The portion 18 is attached firmly to the contact cross arm 22 by means of a generally U-shaped fastening member 24 which extends around the contact cross arm and has its ends bent extending through and bent over the bight portion of the member 18.

Clockwise rotation of the contact cross arm 22 therefore causes clockwise rotation of the contact arm assembly and engagement of the movable contact 16 with 3 the stationary contact 13. Following initial engagement of these contacts slight further rotation of the contact cross arm takes place causing slight compression of the spring 20, providing dependable contact pressure.

The contact-carrying portion 17 of the contact arms are each connected by a flexible conductor or braid to a connecting strap 26, which in turn is connected to a relatively rigid magnet Winding conductor 27 encircling a magnet core member 28 and having its other end connected to the lower end of an elongated bimetallic strip member 29, which in turn. is anchored to the insulating casing by suitable means such as by screw 39.

The upper end of the bimetallic strip 29 is connected by a flexible conductor or braid 31 to a terminal strap 32 which in turn is fixedly attached to a load terminal member 33 positioned in a recess at the load end of the circuit breaker.

The primary current path through the circuit breaker, when the contacts are in the closed circuit position, through one pole thereof, is therefore as follows, beginning with the load terminal 33: from load terminal 33 to conductive strap 32, to flexible conductor 31, through bimetallic strip 29, to magnet winding 27, to connecting strap 26, to flexible conductor 25, to contact-carrying member 17, to movable contact 16, to stationary contact 13, to connecting terminal 14 to line terminal 15.

The magnet core 28 has two irregularly shaped pole pieces 34- fixedly attaehed to the opposite :ends thereof.

A relatively movable armature 35 is also provided, comprising a member formed out of relatively thin sheet metal material and pivotally supported by engagement of the shoulders 36 thereof which rest upon corresponding shoulders or ledges in the insulating casing of the base 10. The armature member 35 has an upstanding portion 37 for purposes described, an intermediate offset portion, and a depending relatively wide portion 38 which is adapted to be attracted to the pole face portions 34 of the magnet to cause tripping in manner to be described.

The armature member 35 is biased for rotation, counterclockwise by means of an elongated leaf-type spring (see FIGURE 1, omitted from FIGURE 2 for clarity) 39 which is rigidly attached to the armature 35 at a point just above the pivot point 36 and which has its lower end extending into engagement with a side ledge portion of the side wall of the insulating casing. The action of the spring 39 is such as to resist movement of the armature member in a clockwise direction and to normally retain it inengagement with a stop surface 40 integral with the insulating casing.

The armature member 35 is therefore supported simply by resting in insulating bearings in the side walls of each chamber and its normal position is determined by insulating surfaces 44) provided in the insulating casing by molding. The normal position of the armature is therefore very closely controlled by the molded-in dimensions of the insulating casing.

In order to protect the bimetallic strip from being adversely affected by short circuit currents, a bypassing circuit is provided comprising a flexible conductor or braid 41 having one end thereof attached to the upper end of the bimetallic strip 29 and having its other end connected to an intermediate portion of the armature 35. A contact 42 is also provided on the armature 35 adapted to coact with a contact 43 mounted on a conducting strap 44 connected to the flexible conductor 25 by means of screw 45.

On the occurrence of high short-circuit currents, the armature member 35 is attracted toward the pole members 34 and the contact 42 touches the contact 43. At this time, therefore, a bypassing circuit is established which shunts the greater portion of such short-circuit current around the bimetallic strip 29 and the magnet 28, directly to the braid 25 and the movable contact.

For the purpose of operating the contact cross arm i 22 and tis associated contact arm assemblies between open and closed circuit positions manually as desired and automatically upon the occurrence of predetermined current conditions in the circuit through such contacts, an operating mechanism is provided, as shown particularly at FIGURES 3-5. The mechanism comprises a pair of opposed side plates 59 and 51, see FIGURE 5, which are generally planar throughout the major portion thereof but have the right-hand portion as viewed return-bent to form a U-shaped section as shown particularly at FIGURE 5A. The return- bent portions 52 and 53 are spaced apart a short distance to receive a releasable trip member 54 and the parts having aligned openings therein through which a pivot pin 55 extends. The pivot pin 55 has its opposite ends headed over to attach these parts permanently together at this point. The return-bents 53 each also include a projection 56 for a purpose to be described.

The operating mechanism includes a pair of interconnected toggle links 57 and 58, pivotally connected respectively tothe releasable trip member at 59 and to the center contact arm assembly at 60, the pivot pin 60 being the same pivot pin which interconnects the two portions of the center contact arm.

The releasable trip member 54 includes a latching projection 61 which is normally in engagement with a bent-over portion 62 of an intermediate latch member 63, pivotally supported between the side walls of .the mechanism on pin 64. The latch member 63 has a lower extension portion 65 for resetting purposes in a manner to be described. The intermediate latch member 63 is normally held in the position shown in FIGURE 3 by the engagement with a latch member 66, pivotally supported between the sides of the mechanism upon a pivot pin 67. The latch member 66 has an upstanding portion 68 adapted to be engaged by a current responsive member such as a bimetallic strip or an electromagnetic armature, and has a latch-retaining portion 69 which normally engages the edge of the portion 62 by projecting into an opening 76 in the latch member 63.

It will therefore be observed that upward or clockwise rotation force of the releasable trip member 54 exerts a counterclockwise bias onthe intermediate latch member 63. The latch member 63 is prevented from rotating in a counterclockwise direction, however, by its engagement with the portion 69 of the latch member 66.

The toggle members 57 and 58 are operated between collapsed and straightened positions to move the movable contact between corresponding open and closed circuit positions, by means of overcenter tension-type springs 71 which are connected between the bight portion of a genenally U-shaped handle support member 72 and the knee point 73 of the toggle linkage. The lower ends of the tension springs 71 are connected to the knee point 73 of the toggle linkage by means of a saddle shaped connecting member 74 comprising two interconnected generally U-shaped portions. The handle supporting member 72 is pivot-ally supported on lugs 75 bent outwardly from the mechanism side portions 56 and 51.

For the purpose of facilitating manual operation of the circuit breaker, a manually engageable handle portion 76 is provided, of insulating material, having an enlarged base portion and an upstanding handle portion. The base portion of the handle member 76 includes an aperture 77 through which a lug portion 78 of the handle support member 72 extends. An anchoring screw 79 extends through the bight portion of the handle support member 72 and into threaded engagement with the handle member 76. It will be observed that the handle member 76 is thereby rigidly and fixedly supported on the handle supporting member 72 by the use of only a single screw. The base portion or" the handle member 76 is normally covered by a sliding shield of insulating material as shown particularly in FIGURE 2, which is adapted to close the handle opening in the top portion of the circuit breaker casing in all positions of the operating handle.

The operation of the circuit breaker mechanism will be observed from FIGURE 3 and FIGURE 4. In FIG- URE 3, the circuit breaker mechanism is shown in the off position in solid lines and in the on position in dotted lines. 'It will be observed that as the handle 76 is moved from the o and toward the on position, the tension springs 71 pass overcenter across the line of centers of the pins 59 and 73, and cause the upper toggle link 57 to rotate in a counterclockwise direction about its pivotal support on the releasable trip member 54, thereby straightening the toggle linkage and moving the contact arm to closed circuit position. The toggle link 57 is stopped in its forward movement by engagement with a pin 79 carried by the releasable trip member 54.

When the releasable trip member 54 is released by action of a current responsive device as described above, the action of the tension springs 71 is such as to draw the toggle knee pivot pin 73 of the toggle linkage upwardly toward the handle, thereby rotating the trip member 54 clockwise about its pivotal support 55 and moving the contact arms to open position as shown in FIGURE 4. The movement of the releasable trip member 54 clockwise is limited by the engagement of the pin 79 with the projection 56 carried by the portions 52, 53 of the mechanism side plates. In addition, as the trip member 54 starts to rotate clockwise upon being released from the intermediate latch 63, the pin 79, which is in engagement with the forward edge of the upper toggle link 57, moves slightly to the left as viewed in FIGURE 3 and assists in the opening action by starting a collapsing action of the toggle linkage.

As the pin 73 moves upwardly under the influence of the springs 71, it also moves toward the left and thereby changes the line of action of the springs 71 with respect to the pivot point 75 of the handle support member 72 and causes the handle support member 72 to move counterclockwise. The counterclockwise movement of the handle support member 72 is limited by the engagement of pin 81 carried by the handle support member 72 with the edge portion 82 of the releasable trip member 54, in which position, the parts come to rest. Overtravel or Whipping of the contact-carrying portions 17 of the two outside poles is restricted by the provision of abutments 17a molded integral with the casing cover '11.

In order to reset and reclose the circuit breaker mechanism, the handle is moved manually toward the off position during which movement the pin 81 carried by the handle support member 72, engages the edge portion 82 of the releasable trip member 54 and likewise rotates it in a counterclockwise direction until the latch end portion 61 thereof is below the latch retaining portion 62 of the intermediate latch member 63. Slight further counterclockwise movement of the handle 72 causes the knee portion of the toggle linkage 57 and S8 to engage the extension 65 of the intermediate latch member 63, thereby rotating the intermediate latch member 63 in clockwise direction so that the latch retaining portion 62 overlies the latch portion 64 of the releasable trip member. The latch member 66 is then free to rotate slightly counterclockwise under the bias of latch return spring 84 to again retain the latch portion 62 in latching position. The breaker may thereafter be returned to the on position.

It will be observed that because of dimensional limitations, the releasable trip member 54 is not long enough, nor is sufiicient counter rotation of the handle member 72 possible, to cause resetting of the latch member 62 by means of the end portion of the trip member. Instead, use is made of the knee portion of the toggle linkage to perform this function, thus making possible an extremely compact mechanism.

The side plate members 50 and 51 of the mechanism are retained on the insulating base 10 by suitable means such as by screws 86 which enter into lanced out threaded portions 87 of the side plates. It will be observed that the positioning of the side plates with respect to the insulating base is determined by the lower edge of the side frames, and that no bending-over is necessary to attach these parts. This afifords an important advantage, since the dimensions which are determined by stamping out of a piece of metal in the flat condition can be extremely closely controlled, while those involved or affected by bending of the metal cannot be very Well controlled. By utilizing side mechanisms which are identical in the stamped or flat condition and mounting them on the insulating base with a blanked edge as the determining dimensional factor, accurate transverse alignment of these parts is assured. This assures also that there will be no tilting or cooking of the mechanism, which would be very undesirable because of the limited space involved, and also makes it possible to use only a single joining member to attach the two-side plate portions of the mechanism together, i.e., pin 55, it being observed that none of the other pins which are positioned between the sides of the casing are headed-over or include retaining elements.

The contact cross arm 22 is pivotally supported by being inserted into open end notches 87 in the side plates 59 and 51. This restrains the contact cross arm from movement vertically toward and away from the back wall of the circuit breaker casing. The contact shaft cross arm 22 is retained from movement horizontally, that is, parallel to the back wall of the circuit breaker by engagement of portions thereof with corresponding vertical bearing portions provided integral with the insulating casing. Such bearing surfaces are shown, for example, in FIG- URE 1 at 89 in the outer side wall of the casing and also at 89 in the insulating barrier portion between the two adjacent recesses. This construction greatly simplifies the assembly of the mechanism and the circuit breaker, since it is only necessary to insert the contact cross arm in the notches 87 of the side mechanism plates and then to insert the assembled mechanism into the insulating base of the circuit breaker and to anchor it there n. Thereafter, the contact cross arm is closely retained from movement in all directions by the various bearing surfaces mentioned.

The common trip bar 66 is pivotally supported upon a shaft 67 which is provided with a pair of intermediate non-circular portions which are adapted to fit into the slots 90 in the mechanism side plates and then to be rotated into final position in the enlarged portion of the slots. Thereafter it cannot be removed from its position since it is not possible to rotate the trip member sufficientiy after insertion in the circuit breaker casing.

In FIGURE 6 there is shown a modification of the invention which is adapted for use in a single-pole circuit breaker. In this form of the invention, the intermediate latch member 63 is omitted and instead the latch member 11 is pivotally supported on a pin 111 in the side frame members of the mechanism and is biased by a tension type spring 112 in a counterclockwise direction. The latch member includes an intermediate lanced-out latch portion 113 which engages the latching end 61 of the releasable trip member 54. Upon deflection of the bimetallic strip 114, the screw 115 carried thereby engages the upper end of the trip member of the latch 110 and rotates it clockwise, withdrawing the latch 113 from the tripped member 54 and causing tripping. A magnetic trip member is also provided, including a generally U- shaped field piece 116 rigidly attached to the bimetallic strip 114 and adapted to attract the lower end of the latch member 119 as an armature, to likewise cause tripping. In order to provide a bypassing circuit to protect the bimetallic strip 114 in a manner similar to that described above, a pair of shorting contacts 117 are provided, one of which is carried in insulated relation on the latch member 116 and connected by a flexible conductor or braid, not shown, to the upper end of the bimetallic strip 114. The other of the shorting contacts 117 is carried by a resilient conductive strip member 118 which is connected to the conductive braid 119 leading to the movable contact.

While I have shown only specific forms of my invention, it will be readily'appreciated that many modifications thereof may be made by those skilled in the art, and I therefore intend by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention. 7

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

1. An electric circuit breaker comprising a base of insulating material having a bottom wall, at least one pair of opposed side waiis and an open top Wall, a relatively stationary contact supported in said insulating base on said bottom wall, a relatively movable contact supported for movement in said insulating base into and out of engagement with said stationary contact, a contact cross arm extending transversely of said insulating base and supporting said movable contact thereon, operating means for said movable contact comprising a pair of opposed side plates, a horizontally elongated aperture in each of said side plates, a vertically elongated recess in each of said opposed side walls of said insulating base extending from said open top wall toward said bottom wall, said contact cross-arm being retained for rotation about a substantially fixed axis in said insulating base by cooperative engagement with opposed top and bottom edge surfaces of said horizontal apertures in said side plates and with opposed front and back surfaces of said vertical recesses in said opposed side Walls of said insulating base, and means attaching said opposed side plates second pole chamber at one side of said first pole chamher said pole chambers having a common side Wall and each of said pole chambers having an outer side wall in spaced parallel reiation to said common side wall, said pole chambers having a bottom wall and an open top wall, at least one relatively stationary contact in each 'of said pole chambers, at least one relatively movable con tact supported for movement in each of said pole chambers into and out of engagement with said stationary contacts respectively, a contact cross-arm extending transversely of said insulating base across both of said pole chambers and supporting said movable contacts thereon for movement in unison, operating means for said contact cross-arm in one of said chambers comprising a pair of opposed side plates, a horizontally extending elongated aperture extending inwardly from one edge of each of said side plates, a vertically extending elongated recess extending downwardly from one edge of each of said outer walls, a vertically extending slot in said common wall in alignment with said recesses, said contact crossarrn being retained for rotation about a substantially fixed axis in said insulating base by cooperative engagement with opposed top and bottom edge surfaces of said apertures in said side plates and said opposed front and back surfaces of said recessesin said outer walls, and with front and back surfaces of said slot in said common wall, and means attaching said opposed side plates to said insuiating base.

References Cited in the file ofthis patent UNITED STATES PATENTS 2,204,409 Gano June 11, 1940 2,376,759 Dyer et al. May 22, 1945 2,646,127 Rowe etal. May 26, 1953 FOREIGN PATENTS 775.450 Great Britain May 22, 1957

Claims (1)

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING A BASE OF INSULATING MATERIAL HAVING A BOTTOM WALL, AT LEAST ONE PAIR OF OPPOSED SIDE WALLS AND AN OPEN TOP WALL, A RELATIVELY STATIONARY CONTACT SUPPORTED IN SAID INSULATING BASE ON SAID BOTTOM WALL, A RELATIVELY MOVABLE CONTACT SUPPORTED FOR MOVEMENT IN SAID INSULATING BASE INTO AND OUT OF ENGAGEMENT WITH SAID STATIONARY CONTACT, A CONTACT CROSS ARM EXTENDING TRANSVERSELY OF SAID INSULATING BASE AND SUPPORTING SAID MOVABLE CONTACT THEREON, OPERATING MEANS FOR SAID MOVABLE CONTACT COMPRISING A PAIR OF OPPOSED SIDE PLATES, A HORIZONTALLY ELONGATED APERTURE IN EACH OF SAID SIDE PLATES, A VERTICALLY ELONGATED RECESS IN EACH OF SAID OPPOSED SIDE WALLS OF SAID INSULATING BASE EXTENDING FROM SAID OPEN TOP WALL TOWARD SAID BOTTOM WALL, SAID CONTACT CROSS-ARM BEING RETAINED FOR ROTATION ABOUT A SUBSTANTIALLY FIXED AXIS IN SAID INSULATING BASE BY COOPERATIVE ENGAGEMENT WITH OPPOSED TOP AND BOTTOM EDGE SURFACES OF SAID HORIZONTAL APERTURES IN SAID SIDE PLATES AND WITH OPPOSED FRONT AND BACK SURFACES OF SAID VERTICAL RECESSES IN SAID OPPOSED SIDE WALLS OF SAID INSULATING BASE, AND MEANS ATTACHING SAID OPPOSED SIDE PLATES TO SAID BOTTOM WALL OF SAID INSULATING BASE.

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