IE56136B1 - Circuit breaker with improved cross-bar and contact assembly - Google Patents

Abstract

The invention relates to an electric circuit breaker having improved operating means with current-limiting capability. The operating means include an insulating cross-bar (84) pivotally supporting one contact (52) of each contact pair and having, at each pivotal connection (110) with a contact, a portion (270) defining a pocket (282) into which extends an end portion (284) of the associated contact, and in which are disposed restraining means (286, 288) cooperating with said end portion in such manner as to normally constrain the contact (52) to move together and in unison with the cross-bar (84), and to permit the contact to open independently of the cross-bar under the action of electrodynamic forces resulting from a high-level fault current flowing through the contacts. The cross-bar assembly is compact, requiring relatively little space, and at the same time provides reliable and fast contact operation.

Description

The invention relates to an electric circuit breaker comprising at least one pair of cooperating contacts, and operating means including an insulating cross-bar which pivotally supports a movable contact of said or each pair and is pivotally supported for movement between a contact-open position and a contact-closed position, said cross-bar having, at its pivotal connection with each movable contact thereon, a portion which defines a pocket receiving an end portion of said movable contact and associated restraining means including a spring and cooperating with said contact end portion in such manner as to normally constrain the contact to move together and in unison with the cross-bar, and fo permit the contact fo move to the contact-open position independently of the cross-bar and under the action of over-current induced electrodynamic force when exceeding a predetermined level.

The operating mechanism of such circuit breakers Includes an over-center toggle mechanism to open at least one pair of electrical circuit breaker contacts. A trip mechanism is used for controlling the movement of the over-center toggle mechanism fo separate the contacts upon an overload condition or upon a short circuit or fault current condition. Xn addition, some prior art circuit breakers use blow-aparf contacts to rapidly interrupt the flow of high level short circuit or fault current for protecting an electrical system against overload and fault current conditions.

Examples of such circuit breakers with a blow-apart facility for separating the contacts are disclosed in US—Patent 4 067 767 and in British Patent 1 564 412. British Patent 1 564 412 discloses a circuit breaker as defined above, wherein the restraining means disposed in the pocket of the cross-bar has a compression spring and a plunger member with a curved end extending into an arcuate indent in the rear end portion of the movable contact. ^hen a blow-apart movement of the movable contact relative to the cross-bar occurs due to a short-circuit or fault current condition, the compression spring with the plunger is tilted from its normal position through a certain angle to an over-center position with the aim to arrest the movable contact in its blown-back position. However, because the blow-apart movement of the movable contact produced by the over-current induced electrodynamic forces will occur very rapidly, a re-striking movement of the movable contact is likely to occur unless the blown-back movable contact is arrested in a sufficiently stable condition which, however, may not be ensured with said prior art arrangement.

Accordingly, it is the object of the present invention to provide an improved dimensionally small molded case circuit and reliable operation - 3 breaker capable of fast, effective avoiding any restriking movement of the blow-open movable contact.

According to one aspect the Invention is characterised in that 5 said restraining means comprise a spring follower with a first portion thereof pivotally seated against a surface of th® cross-bar, and with a second portion which is resiliently biased against said contact end portion of the associated movable contact by a compression spring, and in that said contact end portion has a surface which, upon independent movement of th® movable contact to said contact-open position, cooperates with said second portion of the spring follower to hold said movable contact in the contact-open position, movement of the cross-bar to the contact-open position being effective to disengage said surface from said second spring follower portion.

According to another aspect the invention is characterised in that said restraining means comprise an open slot formed in said contact end portion, and a spring-biased pin normally engaged in said open slot, the latter having a configuration * causing the spring-biased pin to be cammed out of th® slot, and thereby to release the associated contact for independent movement in the contact-open position under said electrodynamic force, when the latter exceeds said 'predetermined value, and that said movable contact has associated therewith a latch which cooperates with said contact end portion to hold the latter in the contact-open position upon independent movement of the contact thereto, the arrangement being such that subsequent movement of the cross5 bar in said contact-open position disengages said contact end portion from the latch and thereby renders the latter ineffective.

According to a further aspect the Invention is characterised in that said restraining means comprise a pin disposed on said contact end portion, and a torsion spring having a free spring arm thereof resiliently engaged with said pin so as to normally urge the movable contact toward the contact-closed position, the location of said pin relative to the pivot axis of the associated contact being such that independent movement of the movable contact in the contact-open position will cause the pin to ride on the free spring arm to a position enabling the latter to hold the contact in said contact-open position and that subsequent movement of the cross-bar to said contactopen position will cause the pin to return upon said free spring arm to its normal position.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:* 5 Fig. 1 is a cross-sectional view of a circuit breaker depicting the device in its COPJT^CT-CLOSED and BLOWT-OPW positions; Fig. 2 is an exploded, perspective view of portions of the operating mechanism of the device of Fig. 1; Fig. 3 is a fragmentary, cross-sectional view of the center pole or phase of the device of Fig. 1, depicting the contacts of the device in their OPEH position; Fig. 4 is a fragmentary, cross-sectional view of the center pole or phase of the device of Fig. 1, depicting the device in its TRIPPED position; Fig. 5 is a fragmentary, cross-sectional view of an alternative embodiment of the device of Fig. 1, depicting the contacts of the device in their CLOSED and BLOW-OPE^ positions; Fig. 6 is a fragmentary, plan sectional view of the device of Fig. 5 taken along line 6—6 of Fig. 5; Fig. 7 is a fragmentary, cross-sectional view of the device of Fig. 5, depicting the device in its TRIPPED position; - 6 Fig. 8 is a fragmentary, cross-sectional view of an alternative embodiment of the device of Fig. 1, depicting the contacts of the device in its CLOSED and BL0&3N-0PEN positions; Fig. 9 is a fragmentary, plan sectional view of the device of Fig. 8 taken along line 9-9 of Fig. Q; and Fig. 10 is a fragmentary, cross-sectional view of the device of Fig. 8, depicting the device in its TRIPPED position.

Referring to the drawings and initially to Figs. 1—4, there is illustrated a molded case circuit breaker 30 embodying the invention. Although the circuit breaker 30 is depicted and described herein as a three-phase or three-pole circuit breaker, the invention is equally applicable to single-phase or other polyphase circuit breakers, and to both AC circuit breakers and DC circuit breakers.

The circuit breaker 30 includes a molded, electrically insulating cover 32 secured to a molded, electrically insulating base 34 by a plurality of fasteners 36. A plurality of first electrical terminals or line terminals 38 are provided, one for each pole or phase, as are a plurality of second electrical terminals or load terminals 40. These 'terminals are used to serially connect the circuit breaker 30 electrically info a three-phase electrical circuit for protecting a three-phase electrical system.

The circuit breaker 30 further includes an electrically insulating operating handle 42 extending through an opening 44 in the fop cover 32 for setting the circuit breaker 30 fo its CLOSED position (Fig. 1) or fo its OPEM position (Fig. 3). The circuit breaker 30 also may assume a BLGffi-OPEK position (Fig. 1, dotted line position) or a TRIPPED position (Fig. 4). Subsequent to being placed in its TRIPPED position, the circuit breaker 30 may be reset fo further protective operation by moving the handle 42 from its TRIPPED position (Fig. 4) pasts its OPEN position (Fig. 3). The handle 42 may then be left in its OPEN position (Fig. 3) or moved fo its CLOSED position (Fig. 1), in which case the circuit breaker 30 is ready for further protective operation. The movement of the handle 42 may be achieved either manually or automatically by a machine actuator. Preferably, an electrically insulating strip 46, movable with the handle 42, covers the bottom of the opening 44 and serves as an electrical barrier between the interior and the exterior of the circuit breaker 30.

As its major internal components, the circuit breaker 30 includes a lower electrical contact 50, an upper electrical contact 52, an electrical arc chute 54, a slot motor 56, and an operating mechanism 58. The arc chute 54 and the slot motor 56 are conventional, per se, and thus are not·discussed - 8 in detail hereinafter. The slot motor 56, consisting either of a series of generally U-shaped steel laminations encased in electrical insulation or of a generally U-shaped, electrically insulated, solid steel bar, is disposed about the contacts 50 and 52 to concentrate the magnetic field generated upon a high-level short circuit or fault current condition, thereby greatly increasing the magnetic repulsion forces between the separating electrical contacts 50 and 52 to rapidly accelerate the separation of electrical contacts 50 and 52. The rapid separation of the electrical contacts 50 and 52 results in a relatively high arc resistance to limit the magnitude of the fault current.

The lower electrical contact 50 (Fig. 1) includes a lower, formed, stationary member 62 secured to the base 34 by a fastener 64, a lower movable contact arm 66, a pair of contact compression springs 53, a lower contact biasing means or compression spring 70, a contact 72 for physically and electrically contacting the upper electrical contact 52, and an electrically insulating strip 74 to reduce the possibility of arcing between the upper electrical contact 52 and portions of the lower electrical contact 50. The line terminal 38 extending exteriorly of the base 34 comprises an integral end portion of the member 62. The member 62 includes an inclined portion 62A that serves as a lower limit or stop for the moving contact arm 66 during its blow-open operation, an 'aperture 62b overlying a recess 76 formed in the base 34 for - 9 seating the compression spring 70; and a lower flat section 62C through which the aperture 62B is formed. The flat section 62C may also include a threaded aperture 62D formed therethrough for receiving the fastener 64 to secure the stationary member 62 and thus the lower electrical contact 50 to the base 34. The stationary member 62 includes a pair of spaced apart, integrally formed, upstanding generally curved or ΰ-shaped contacting portions S2F. The contacting portions 62F each include two, spaced apart, flat, inclined surfaces 62G and 62h, inclined at an angle of approximately 45 degrees to the plane of the lower flat section 52C and extending laterally across the inner surfaces of the contacting portions 62F. A stop 62J is provided for limiting the upward movement of the contact arm 66.

The contact arm 66 is fixedly secured to a rotatable pin 78 for rotation therewith within the curved contacting portions 62F about the longitudinal axis of the rotatable pin 78. The lower movable contact arm 66 includes an elongated rigid lever arm 66A extending between the rotatable pin 78 and the contact 72, and downwardly protuberant portion or spring locator 66B for receipt within the upper end of the compression spring 70 for maintaining effective contact between the lower movable arm 66 and the compression spring 70. Finally, the lower movable contact arm 66 includes an integrally formed, flat surface 66C formed at its lower end for contacting the stop - 10 62J to limit the upward movement of the lower movable contact arm 66 and the contact 72 fixedly secured thereto.

The lower electrical contact 50 as described hereinabove utilizes the high magnetic repulsion forces generated by high level short circuit or fault current flowing through the elongated parallel portions of the electrical contacts 50 and 52 to cause the rapid downward movement of the contact arm 66 against the bias of the compression spring 70. An extremely rapid separation of the electrical contacts 50 and 53 and a resultant rapid increase in the resistance across the electrical arc formed between the electrical contacts 50 and 52 is thereby achieved, providing effective fault current limitation within the confines of relatively small physical dimensions.

The operating mechanism 58 includes an over-center toggle mechanism 80; a trip mechanism 82; and integral or one-piece molded cross-bar 84 (Fig. 2); a pair of rigid, opposed or spaced apart, metal side plates 86; a rigid, pivotable, metal handle yoke 86; a rigid stop pin 90; and a pair of operating tension springs 92.

The over-center toggle mechanism 80 includes a rigid, metal cradle 96 that is rotatable about the longitudinal central axis of a cradle support pin 98. The opposite longitudinal ends of the cradle support pin 98 in an assembled condition are retained in a pair of apertures 100 formed through the side plates 86.

The toggle mechanism 80 further includes a pair of upper toggle links 102, a pair of lower toggle links 104, a toggle spring pin 106 and an upper toggle link follower pin 108. The lower toggle Units 104 are secured to the upper electrical contact 52 by a toggle contact pin 110. Each of the lower toggle links 104 includes a lower aperture 112 for receipt therethrough of the toggle contact pin 110. The toggle contact pin 110 also passes through an aperture 114 formed through the upper electrical contact 52 enabling the upper electrical contact 52 to freely rotate about the central longitudinal axis of the pin 110. The opposite longitudinal ends of the pin 110 are received and retained in the cross-bar 84. Thus, movement of the upper electrical contact 52 under other than high level short circuit or fault current conditions and the corresponding movement of the cross-bar 84 is effected by movement of the lower toggle links 104. Xn this manner, movement of the upper electrical contact 52 by the operating mechanism 58 in the center pole or phase of the circuit breaker 30 simultaneously, through the rigid cross-bar 84, causes the same movement in the upper electrical contacts 52 associated with the other poles or phases of the circuit breaker 30.

Bach of the lower toggle links 104 also includes an upper aperture 116; and each of the upper toggle links 102 includes an aperture 113. The pin 106 is received through the apertures 116 and 118, thereby interconnecting the upper and lower toggle links 102 and 104 and allowing rotational movement therebetween. The opposite longitudinal ends of the pin 106 include journals 120 for the receipt and retention of the lower, hooked or curved ends 122 of the springs 92. The upper, hooked or curved ends 124 of the springs 92 are received through and retained in slots 126 formed through an upper planar or flat surface 128 of the bundle yoke 88. At least one of the slots 126 associated with each spring 92 includes a locating recess 130 for positioning the curved ends 124 of the springs 92 to minimize or prevent substantial lateral movement of the springs 92 along the lengths of the slots 126.

In an assembled condition, the disposition of the curved ends 124 within the slots 126 and the disposition of the curved ends 122 in the journals 120 retain the links 102 and 104 in engagement with the pin 106 and also maintain the springs 92 under tension, enabling the operation of the over-center toggle mechanism 80 to be controlled by and responsive to external movements of the handle 42.

The upper links 102 also include recesses or grooves 132 for receipt in and retention by a pair of spaced apart journals 134 formed along the length of the pin 108. The center portion of the pin 108 is configured to be received in an aperture 136 formed through the cradle 96 at a location spaced by a predetermined distance from the axis of rotation of the cradle 96. Spring tension form the springs 92 retains the pin 108 in engagement with the upper toggle links 102. Thus, rotational movement of the cradle 96 effects a corresponding movement or displacement of the upper portions of the links 102.

The cradle 96 includes a slot or groove 140 having an inclined flat latch surface 142 formed therein. The surface 142 is configured to engage an inclined flat cradle latch surface 144 formed at the upper end of an elongated slot or aperture 146 formed through a generally flat, intermediate latch plate 143. The cradle 96 also includes a generally flat handle yoke contacting surface 150 configured fo contact a downwardly depending elongated surface 152 formed along one edge of the upper surface 128 of the handle yoke 88. The operating springs 92 move the handle 42 during a trip operation, and the surfaces 150 and 152 locate the handle 42 in a TRIPPED position (Fig. 4), intermediate the CLOSED position (Fig. 1) and the OPEN position (Fig. 3) of the handle 42, fo indicate that the circuit breaker 30 has tripped. In addition, the engagement of the surfaces 150 and 152 resets the operating mechanism 58 subsequent to a trip operation by moving the cradle 98 in a clockwise direction against the bias of the operating springs 92 from its TRIPPED position (Fig. 4) to and past its OPEN position (Fig. 3) to enable the relatching of the surfaces 142 and 144.

The cradle 96 further includes a generally flat elongated stop 5 surface 154 for contacting a peripherally disposed, radially outwardly protuberant portion or rigid stop 156 formed about the center of the stop pin 90. The engagement of the surface 154 with the rigid stop 156 limits the movement of the cradle 96 in a counterclockwise direction subsequent to a trip operation (Fig. 4). The cradle 96 also includes a curved, intermediate latch plate follower surface 157 for maintaining contact with the outermost edge of the inclined latch surface 144 of the intermediate latch plate 148 upon the disengagement of the latch surfaces 142 and 144 during a trip operation (Fig. 4). An impelling surface of kicker 158 is also provided on the cradle 96 for engaging a radially outwardly projecting portion or contacting surface 160 formed on the pin 106 upon the release of the cradle 96 to immediately and rapidly propel the pin 106 in a counterclockwise arc from an OPEN position (Fig. 1) to a TRIPPED position (Fig. 4), thereby rapidly raising and separating the upper electrical contact 52 from the lower electrical contact 50.

During such a trip operation, an enlarged portion or projection 162 formed on the upper toggle links 702 is designed to contact the stop 156 with a considerable amount of force provided by the operating springs 92 through the rotating cradle 96, thereby accelerating the arcuate movements of the upper toggle links 102, the toggle spring pin 106 and the lower toggle links 104. In this manner, the speed of operation or the response time of the operating mechanism 58 is significantly increased.

The trip mechanism 82 includes the intermediate latch plate 148, a movable or pivotable handle yoke latch 166, a torsion spring spacer pin 168, a double acting torsion spring 170 a molded, integral or one-piece trip bar 172 (Figs. 3 and 4), an armature 174, an armature torsion spring 176, a magnet 178, a bimetal 180 (Fig. 1) and a conductive member or heater 182.

The bimetal 180 is electrically connected to the terminal 40 through the conductive member 182. The magnet 178 physically » surrounds the bimetal 180 thereby establishing a magnetic circuit to provide a response fo short circuit or fault current conditions. An armature stop plate 184 has a downwardly depending edge portion 186 that engages the upper end of the armature 174 to limit its movement in the counterclockwise direction. The torsion spring 176 has one longitudinal end formed as an elongated spring arm 188 for biasing the upper portion of the armature 174 against movement in a clockwise direction. An opposite, upwardly disposed, longitudinal end 190 of the torsion spring 176 is disposed in one of a plurality of spaced apart apertures (not illustrated) formed through the upper surface of the plate 184. The spring tension of the spring arm 186 may be adjusted by positioning the end 190 of the torsion spring 176 in a different one of the apertures formed through the upper surfaces of the support plate 184.

The bimetal 180 includes a formed lower end 192 spaced by a predetermined distance from the lower end of a downwardly depending contact leg 194 of the trip bar 173 (Fig. 1). The spacing between the end 192 and the leg 194 when the circuit breaker 30 is in a CLOSED position (Fig. 1) may be adjusted to change the response time of the circuit breaker 30 to overload conditions by appropriately turning a set screw 196, access to which may be provided by apertures 198 formed through the fop cover 32. A current carrying conductive path between the lower end 193 of the bimetal 180 and the upper electrical contact 52 is achieved by a flexible copper shunt 200 connected by any suitable means, for example, by brazing, to the lower end 192 of the bimetal 180 and to the upper electrical contact 53 within the cross-bar 84. Xn this manner, an electrical path is provided through the circuit breaker 30 between the terminals 38 and 40 via the lower electrical contact 50, the upper electrical contact 53, the flexible shunt 200, the bimetal 180 and the conductive member 182.

In addition to the cradle latch surface 144 formed at the ‘upper end of the elongated slot 146, the intermediate latch plate 148 includes a generally square shaped aperture 210 (Fig. 2), a trip bar latch surface 212 at the portion of the aperture 310, an upper inclined flat portion 314 and a pair of oppositely disposed laterally extending pivot arms 216 configured fo be received within inverted keystones or apertures 218 formed through the side plates 86. The configuration of the apertures 218 is designed to limit the pivotable movement of the pivot arms 316 and thus of the intermediate latch plate 148.

The handle yoke latch 166 includes an aperture 220 for receipt therethrough of one longitudinal end 222 of the pin 168. The handle yoke latch 166 is thus movable or pivotable about the longitudinal axis of the pin 168. An opposite longitudinal end 234 of the pin 166 and the end 222 are designed fo be retained in a pair of spaced apart apertures 226 formed through the side plates 86. Frior fo the receipt of the end 324 in the aperture 336, the pin 168 is passed through the torsion spring 170 fo mound the torsion spring 170 about an intermediately disposed raised portion 228 of the pin 168. One longitudinal end of the body of the torsion spring 170 is received against an edge 230 of a raised portion 232 of the pin 168 to retain the torsion spring 170 in a proper operating position. The torsion spring 170 includes an elongated, upwardly extending spring arm 234 for biasing the flat portion 214 of the intermediate latch plate 148 for movement in a counterclockwise direction for resetting the intermediate latch plate 148 subsequently to a trip operation by the overcenter toggle mechanism 80 and a downwardly extending spring arm 236 for biasing an upper portion or surface 237 (Fig. 1) of the trip bar 172 against rotational movement in a clockwise direction.

The handle yoke latch 166 includes an elongated downwardly extending latch leg 240 and a bent or outwardly extending handle yoke contacting portion 242 (Fig. 2) that is physically disposed to be received in a slotted portion 244 formed in and along the length of one of a pair of downwardly depending support arms 246 of the handle yoke 88 during a reset operation (Fig. 3). The engagement of the aforementioned downwardly depending support arm 246 by the handle yoke latch 166 prohibits the handle yoke 88 from traveling to its reset position if the contacts 72 and 306 are welded together. If the contacts 72 and 306 are not welded together, the cross-bar 84 rotates to Its TRIPPED position (Fig. 4); and the handle yoke latch 166 rotates out of the path of movement of the downwardly depending support arm 246 of the handle yoke 88 and into the slotted portion 244 to enable the handle yoke 88 to travel to its reset position, past its OPEM position (Fig. 3). An integrally molded outwardly projecting surface 248 on the cross-bar 84 is designed to engage and move the latch leg 240 of the handle yoke latch 166 out of engagement with the handle yoke 88 during the movement of the cross-bar 84 from its OPEN position (Fig. 3) to a CLOSED position (Fig. 1).

The trip bar 172 is formed as a molded, integral or one-piece trip bar 172 having three, spaced apart downwardly depending contact legs 194, one such contact leg 194 being associated with each pole or phase of the circuit breaker 30. In addition, the trip bar 172 includes three, enlarged armature support sections 250, one such support section 250 for each pole or phase of the circuit breaker 30. Bach of the support sections 250 includes an elongated, generally rectangularly shaped slot or pocket 252 formed therethrough (Figs. 1 to 3) for receiving a downwardly depending trip leg 254 of the armature 174. The armature 174 includes outwardly extending edges or shoulder portions 256 for engaging the upper surfaces of the pockets 252 to properly seat the armature 174 in the trip bar 172. Bach trip leg 254 is designed to engage and rotate an associated contact leg 194 of the trip bar 172 in a clockwise direction (Fig. 4) upon the occurrence of a short circuit or fault current condition.

The trip bar 172 also includes a latch surface 258 (Fig. 1) for engaging and latching the trip bar latch surface 212 of the intermediate latch plate 148. The latch surface 258 is disposed between a generally horizontally disposed surface 260 and a separate, inclined surface 262 of the trip bar 172.

The latch surface 258 (Fig. 1) is a vertically extending surface having a length determined by the desired response characteristics of the operating mechanism 58 to an overload condition or fo & short circuit or fault condition. In a specific embodiment of the present invention, an upward movement of the surface 260 of approximately one-half millimetre is sufficient fo unlatch the surfaces 258 and 212. Such unlatching results in movement between the cradle 96 and the intermediate latch plate 148 along the surfaces 142 and 144, immediately unlatching the cradle 96 from the intermediate latch plate 148 and enabling the counterclockwise rotational movement of the cradle 96 and a trip operation of the circuit breaker 30. During a reset operation, the spring arm 236 of the torsion spring 170 engages the surface 237 of the trip bar 172, causing the surface 237 to rotate counterclockwise fo enable the latch surface 258 of the trip bar 172 to engage and relafch with the latch surface 212 of the intermediate latch plate 148 to reset the intermediate latch plate 148, the trip bar 172 and the circuit breaker 30. The length of the curved surface 157 of the cradle 96 should be sufficient fo retain contact between the upper portion 214 of the intermediate latch plate 148 and the cradle 96 fo prevent resetting of the intermediate latch plate 148 and the trip bar 172 until the latch surface 142 of the cradle 96 is positioned below the latch surface 144 of the intermediate latch plate 148. Preferably, each of the three poles or phases of the circuit breaker 30 is provided with a bimetal 180, an armature 174 and a magnet 178 for displacing an associated contact leg 194 of the trip bar 172 as a result of the occurrence of an overload condition or a short circuit or fault current condition in any one of the phases to which the circuit breaker 30 is connected.

Xn addition to the integral projecting surface 248, the cross5 bar 84 includes three enlarged sections 270 (Fig. 2) separated by round bearing surfaces 372. A pair of peripherally disposed, outwardly projecting locators 274 are provided to retain the cross-bar 84 in proper position within the base 3¼. The cross bar 84 is seated for rotational movement in the base 34.

Each enlarged section 270 also includes a window, pocket or fully enclosed opening 282 formed therein (Fig. 2) for receipt of one longitudinal end or base portion 284 of the upper electrical contact 52 (Fig. 1). The opening 282 also permits the receipt and intention of a contact arm compression spring 286 (Fig. 2, and an associated, formed, spring follower 288. The compression spring 286 is retained in proper position within the enlarged section 270 by being disposed about an integrally formed, upwardly projecting boss 390.

The spring follower 288 is configured to be disposed between the compression spring 286 and the base portion 284 of the upper electrical contact 52 to transfer the compressive force from the spring 286 to the base portion 284, thereby ensuring 'that the upper electrical contact 52 and the cross-bar 84 move - 22 in unison. The spring follower 288 includes a pair of spaced apart generally J-shaped grooves 292 formed therein for receipt of a pair of complementarily shaped, elongated ridges or shoulder portions 294 to properly located and retain the spring follower 288 in an enlarged section 270. A first generally planar portion 296 is located at one end of the spring follower 288; and a second planar portion 298 is located at the other longitudinal end of the spring follower 288 and is spaced from the portion 296 by a generally flat inclined portion 300.

The shape of the spring follower 288 enables it to engage the base portion 284 of the upper electrical contact 52 with sufficient spring force to ensure that the upper electrical contact 52 follows the movement of the cross-bar 84 in response to operator movements of the handle 42 or the operation of the operating mechanism 58 during a normal trip operation. However, upon the occurrence of a high level short circuit or fault current condition, the upper electrical contact 52 can rotate about the pin 110 by deflecting the spring follower 288 downwardly (Fig.1), enabling the elecrical contacts 50 and 52 to rapidly separate and move to their BLOW-OPEN positions (Fig. 1) without waiting for the operating mechanism 58 to sequence. This independent movement of the upper electrical contact 52 under the above high fault condition is possible to any pole or phase of the circuit breaker 30. - 23 During normal operating conditions, an inclined surface 302 of the base portion 284 of the upper electrical contact 52 contacts the inclined portion 300 or the junction between the portions 298 and 300 of the spring follower 288 fo retain the cross-bar 84 in engagement with the upper electrical contact 52. However, upon the occurrence of a high level short circuit or fault current condition, the inclined surface 302 is moved past and out of engagement with the portions 298 and 300; and a terminal portion or surface 304 of the base portion 284 engages the downwardly deflected planar portion 298 of the spring follower 288 to retain the upper electrical contact 52 in its BLOW-OPEH position, thereby eliminating or minimizing the possibility of contact restrike. Subsequently, when the circuit breaker 30 trips, the upper electrical contact 52 is forced by the operating mechanism 58 against the stop 156 to reset the upper electrical contact 52 for movement in unison with the cross-bar 84. During this resetting operation, the surface 304 is moved out of engagement with the portion 298 and the inclined portion 302 is moved back into engagement with the spring follower 286. By changing the configuration of the spring follower 288 or the configuration of the surface 302, 304 of the base portion 284 of the upper electrical contact 52, the amount of upward travel of the upper electrical contact 52 during a BLOWM-OPEN operation required fo bring the surface 304 info contact with the spring follower 288 can be altered as desired.

The openings 282 formed in the enlarged sections 270 of the cross-bar 84 permit the passage of the flexible shunts 200 therethrough without significantly reducing the strength of the cross-bar 84. Since the flexible shunts 200 pass through the openings 282 adjacent the axis of rotation of the crossbar 84, minimum flexing of the flexible shunts 200 occurs, increasing the longevity and reliability of the circuit breaker 30.

The upper electrical contact 52 also includes a contact 306 10 for physically and electrically contacting the contact 73 of the lower electrical contact 50 and an upper moveable elongated contact arm 308 disposed between the contact 306 and the base portion 284. It is the passage of high level short circuit or fault current through the generally parallel contact arms 66 and 308 that causes very high magnetic repulsion forces between the contact anas 66 and 308, effecting the extremely rapid separation of the contacts 73 and 306. An electrically insulating strip 309 may be used to electrically insulate the upper contact arm 308 from the lower contact arm 66.

In addition to the aperture 100, 218 and 226, the side plates 86 include apertures 310 for the receipt and retention of the opposite ends of the stop pin 90. In addition, bearing or 'pivot surfaces 312 are formed along the upper portion of the side plates 86 for engagement with a pair of bearing surfaces or round tabs 314 formed at the lowermost extremities of the downwardly depending support arms 246 of the handle yoke 88. The handle yoke 88 is thus controllably pivotal about th® bearing surfaces 314 and 312· The side plates 88 also include bearing surfaces 316 (Fig. 2) for contacting the upper portions of the bearing surfaces 272 of the cross-bar 84 and for retaining the cross-bar 84 securely in position within th® base 34. The side plates 86 include generally C-shaped bearing surfaces 317 configured to engage a pair of round bearing surfaces 318 disposed between the support sections 250 of the trip bar 172 for retaining the trip bar 172 in engagement with a plurality of retaining surfaces integrally formed as part of the molded base 34. Each of the side plates 86 includes a pair of downwardly depending support arms 322 that terminate in elongated, downwardly projecting stakes or tabs 324 for securely retaining the side plates 86 in the circuit breaker 30. Associated with the tabs 324 are apertured metal plates 326 that are configured to be received in recesses. In assembling the support plates 86 in the circuit breaker 30, the tabs 324 are passed through apertures formed through the base 34 and, after passing through the apertured metal plates 326, are positioned in the recesses 328. The tabs 324 may then be mechanically deformed, for eample, by peening, to lock the tube 324 in engagement with the apertured metal plates 326, thereby securedly retaining the side plates 86 in engagement with the base 34.

In operation, the circuit breaker 30 may be interconnected in a three phase electrical circuit via line and load connections to the terminals 38 and 40. The operating mechanism 58 may be set by moving the handle 42 from its TRIPPED position (Fig. 4) as far as possible past its OPW position (Fig. 3) to ensure the resetting of the intermediate latch plate 148, the cradle 96 and the trip bar 173 by the engagement of the latching surfaces 142 and 144 and by the engagement of the latch surfaces 212 and 258. The handle 42 may then be moved from its OPEN position (Fig. 3) to its CLOSED position (Fig. 1) causing the operating mechanism 58 fo close the contacts 72 and 306; and the circuit breaker 30 is then ready for operation in protecting a three phase electrical circuit. If, due to a prior overload condition, the bimetal 180 remains heated and deflects the contact leg 194 of the trip bar 172 sufficiently fo prevent the latching of the surface 212 with the surface 258, the handle 42 will return fo its TRIPPED position (Fig. 4); and the electrical contacts 50 and 52 will remain separated. After the bimetal 180 has returned to its normal operating temperature, the operating mechanism 58 may be reset as described above.

Upon the occurrence of a sustained overload condition, the formed lower end 192 of the bimetal 180 deflects along a clockwise arc and eventually deflects the contact leg 194 of the trip bar 172 sufficiently fo unlatch the intermediate latch plate 148 from the trip bar 172, resulting in immediate relative movement between the cradle 95 and the intermediate latch plate 148 along the inclined surfaces 142 and 144. Th® cradle 96 is immediately accelerated by the operating springs 92 for rotation in a counterclockwise direction (Fig. 1) resulting in the substantially instantaneous movement of fh® upper toggle links 102, the toggle spring pin 105 and the lower toggle links 104. As described hereinabove, the impelling surface or kicker 158 acting against the contacting surface 160 of the pin 106 rapidly accelerates the pin 106 in an upward, counterclockwise arc, resulting in a corresponding upward movement of the toggle contact pin 110 and the immediate upward movement of the upper electrical contact 52 to its TRIPPED position (Fig. 4). Since the base portions 284 of all of the upper electrical contacts 53 are biased by the springs 286 into contact with an inferior surface 330 formed in each opening 282 of the cross-bar 84, the upper electrical contacts 52 move in unison with the cross-bar 84, resulting in the simultaneous or synchronous separation of all three of the upper electrical contacts 52 from the lower electrical contacts 50 in the circuit breaker 30. During this trip operation, any electrical arc that may have been present across the contacts 73 and 306 is extinguished.

During this operation, as a result of the change in the lines of action of the operating springs 92, the handle 42 is moved from its CLOSED position (fig 1) to its TRIPPED position (Fig. 4). As is apparent, if the handle 52 is obstructed or held in its CLOSED position (Fig. 1), the operating mechanism 58 still will respond fo an overload condition or to a short circuit or fault current condition to separate the electrical contacts 50 and 52 as described hereinabove. Furthermore, if the contacts 72 and 306 become welded together, the pin 106 does not move sufficiently to change the line of action of the operating springs 92 (Fig. 1), maintaining the operating springs 92 forward (fo the left) of the pivot surfaces 312 of the side plates 86 and biasing the handle 42 to its CLOSED position so as not to mislead operating personnel as fo the operative condition of the electrical contacts 50 and 52.

Upon the occurrence of a short circuit or fault current condition, the magnet 178 is immediately energized fo magnetically attract the armature 174 info engagement with the magnet 178, resulting in a pivotable or rotational movement of the trip leg 254 of the armature 174 in a clockwise direction (Fig. 1) against the contact leg 194 of the trip bar 172. The resultant rotational movement of the contact leg 194 in a clockwise direction releases the intermediate latch plate 148 causing a trip operation as described hereinabove.

Upon the occurrence of a high level short circuit or fault current condition and as a result of the large magnetic repulsion forces generated by the flow of fault current through the generally parallel contact arms 66 and 308, the electrical contacts 50 and 53 rapidly separate and move to their BLOM-OPEM positions (depicted in dotted line form in Fig. 1). While the compression spring 70 returns the contact arm 66 of the lower electrical contact 50 to its OPEN position (Fig. 3), the contact arm 308 is held in its BLOW-OPES^ position by the engagement of the surfaces 304 and 398 as described hereinabove. The reparation of the electrical contacts 50 and 52 is achieved without the necessity of the operating mechanism 58 sequencing through a strip operation.

However, the subsequent sequencing of the operating mechanism 58 through a trip operation forces the upper contact arm 308 against an electrical insulation barrier 332 and the stop 156 in the center pole or phase of the circuit breaker 30 or against steps integrally formed in the top cover 32 in the outer poles or phases of the circuit breaker 30 to cause relative rotational movement between the upper electrical contact 52 and the cross-bar 84, resulting in the reengagement of the inferior surface 330 of the cross-bar 84 by the base portion 284 of the upper electrical contact 53 and the resultant separation of the other electrical contacts 50 and 52 in the other poles or phases of the circuit breaker 30.

In accordance with an alternative embodiment (Figs. 5 through 7) of the circuit breaker 30, an upper electrical contact 410 include a longitudinal end or base portion 412 having a generally J-shaped slot 414 formed therein. The slot 414 received a portion of an elongated spring biased locking pin - 30 416 that is disposed against the forward edges of a pair of elongated slots 418 formed through a pair of opposed or spaced apart sidewalls 420 of an enlarged section 270 of the molded cross-bar 84. Preferably, an upper, outermost point or edge 422 of the slot 414 engages or contacts the outer periphery of the pin 416 at a distance less than halfway along the diameter of the pin 416 to ensure that upon the occurrence of a high level short circuit or fault current of sufficient amperage, an upper, elongated movable contact arm 424 of the electrical contact 410 will be able fo freely rotate about the pin 110 to assume a BLO^N-OFEN position (depicted in dotted line form in Fig. 5). Normally, the pin 416 is kept in engagement with the forward portion or surface of the slots 418 by a pair of tension springs 426 fixedly secured fo the sidewalls 420 by a pair of spring pins 428. Thus, the pin 416 is at least partially received within the slot 414 fo cause the movement of the cross bar slot 84 in unison with the movement of the upper electrical contact 410.

Upon the occurrence of a high level short circuit or fault current of sufficient amperage, the magnetic repulsion forces established by the flow of fault current through the generally parallel contact arms 66 and 424 are sufficient fo move the contact edge 422 along the outer periphery of the pin 416, resulting in a rearward displacement of the pin 416 against the force of the tension springs 426. Fault currents of sufficient amperage can disengage the base portion 412 of the upper electrical contact 410 from the pin 416, thereby enabling the substantially unimpeded upward rotation of the upper contact arm 424. A lower contact point at edge 430 is designed to downwardly deflect th® free end of an elongated leaf spring 432 secured to the base 34 by a fastener 434. After deflecting the leaf spring 432, the upper electrical contact 410 assumes its BLQW-0PEN position (Fig. 5). Subsequent contact between the upper electrical contact 410 and the lower electrical contact 50 is prevented by the engagement of the free end of the leaf spring 432 with the base portion 412 in the region of the slot 414.

A subsequent trip operation of the operating mechanism 56 lifts the upper electrical contact 410 from its BLOW-OPEN position, removing the lock out feature of the leaf spring 432. During such a strip operation, the upper contact arm 424 is forced against the barrier 332 and the stop 156 in the center pole or phase of the circuit breaker 30 or against stops integrally formed in the top cover 32 in the outer poles or phases of the circuit breaker 30 while the cross-bar 64 is rotating in a clockwise direction, thus bringing the pin 416 into engagement with an inclined or contoured surface 436 of the base portion 412. By following along the contoured surface 436, the pin 416 is deflected rearwardly in the slot 418 until it passes the contact edge 422 and snaps forward in the slot 414. In this manner, the molded cross-bar 64 and the - 32 upper electrical contact 410 are reset for subsequent normal movement in unison.

In accordance with a further alternative embodiment (Figs. 8 through 10) of the circuit breaker 30, an upper electrical contact 450 includes a longitudinal end or base portion 452 with an elongated step pin 454 fixedly secured thereto and outwardly projecting in opposite directions therefrom. The stop pin 454 is positioned on the base portion 452 to engage and load an upper, elongated free end or spring arm 456 of one or more torsion springs 458. An opposite, elongated lower end or spring arm 460 engages and is loaded by an interior lower surface 462 of the opening 282 formed in the molded cross-bar 84. The torsion springs 458 are disposed and retained in position by a spring mounting pin 454 fixedly secured in a pair of opposed or spaced apart sidewalls 466 of the cross-bar 84. Thus, during normal operation, the stop pin 454 loads the spring arm 456 with a force at a distance relatively close to the fulcrum of the torsion springs 458. In this manner, the upper electrical contact 450 is caused to move in unison with movements of the cross-bar 84. However, in the presence of a high level short circuit or fault current of sufficient amperage, the repulsion forces present as a result of the flow of fault current through the electrical contacts 50 and 450 cause the rapid separation of the electrical contacts 50 and 450 prior to a trip operation of the operating mechanism 58. During such an occurrence, the stop pin 454 upon the clockwise rotation of the upper electrical contact 450 moves forwardly along the spring arm 456, increasing the distance between the location of the stop pin 454 and the fulcrum of the torsion springs 458, thereby decreasing the spring force applied by the spring arm 456 against the stop pin 454. However, the reduced spring force is sufficient to retain the upper electrical contact 450 In its BL0W-0PE& position (depicted in doffed line form in Fig. 8). During a trip operation by the operating mechanism 58, the upper electrical contact 450 is forced against the barrier 332 and the stop 156 during a clockwise rotational movement of the cross-bar 84, causing the consequent rearward movement of the stop pin 454 along the spring arm 456, decreasing the distance between the stop pin 454 and the fulcrum of each torsion spring 458 and reestablishing the normal spring load between the stop pin 454 and the spring arm 456. The upper electrical contact 450 and the cross-bar 84 are thus reset for movement in unison. 1. An electric circuit breaker comprising at least one pair of cooperating contacts, and operating means including an insulating cross-bar which pivotally supports a movable contact of said or each pair and is pivotally supported for movement between a contact-open position and a contact-closed position, said cross-bar having, at its pivotal connection with each movable contact thereon, a portion which defines a pocket receiving an end portion of said movable contact and associated restraining means including a spring and cooperating with said contact end portion xn such manner as fo normally constrain the contact fo move together and in unison with the cross-bar, and to permit the contact fo move fo the contact-open position independently of the cross-bar and under the action of over-current Induced electrodynamic force when exceeding a predetermined level, characterized in that said restraining means comprise a spring follower with a first portion thereof pivotally seated against a surface of the cross-bar, and with a second portion which is resiliently biased against said contact end portion of the associated movable contact by a compression spring, and in that said contact end portion has a surface which, upon independent movement of the movable contact to said contact-open position, cooperates with said second portion of the spring follower to hold said movable contact in the contact-open position, movement of the cross-bar fo the contact-open position being - 35 effective to disengage said surface from said second spring follower portion.

Claims (1)

1. An electric circuit breaker comprising at least one pair of cooperating contacts, and operating means including an insulating cross-bar which pivotally supports a movable contact of said or each pair and is pivotally supported for movement between a contact-open position and a contact-closed position, said cross-bar having, at its pivotal connection with each movable contact thereon, a portion which defines a pocket receiving an end portion of said movable contact and associated restraining means including a spring and cooperating with said contact end portion in such manner as to normally constrain the contact to move together and in unison with the cross-bar, and to permit the contact to move in the contact-open position independently of the cross-bar and under the action of over-current induced electrodynamic force when exceeding a predetermined level, characterized in that said restraining means comprise an open slot formed in said contact end portion, and a spring-biased pin normally engaged in said open slot, the latter having a configuration causing the spring-biased pin to be cammed out of the slot, and thereby to release the associated contact for independent movement in the contact-open position under said electrodynamic force, when the latter exceeds said predetermined value, and that said movable contact has associated therewith a latch which cooperates with said contact end portion to hold the latter in - 36 the contact-open position upon independent movement of the contact thereto, the arrangement being such that subsequent movement of the cross-bar in said contact-open position disengages said contact end portion from the latch and thereby 5 renders the latter ineffective. 3. An electric circuit breaker according to claim 2, characterized in that said spring-biased pin extends through, and is guided in, elongate openings formed in sidewalls of the associated pocket-defining portion of the cross-bar and is 10 biased by means of two tension springs anchored to said sidewalls and connected to the pin adjacent opposite ends thereof. 4. An electric circuit breaker according to claim 2 or 3, characterized in that said latch comprises a leaf spring 15 having a fixed portion thereof secured in place, and having a free portion which cooperates with said end portion of the associated contact. 5. An electric circuit breaker comprising at least one pair of cooperating contacts, and operating means including an 20 insulating cross-bar which pivotally supports a movable contact of said or each pair and is pivotally supported for movement between a contact-open position and a contact-closed position, said cross-bar having, at its pivotal connection with each movable contact thereon, a portion which defines a - 37 pocket receiving an end portion of said movable contact and associated restraining means including a spring and cooperating with said contact end portion in such manner as to normally constrain the contact to move together and in unison 5 with the cross-bar, and to permit the contact to move to the contact-open position independently of the cross-bar and under the action of over-current induced electrodynamic force when exceeding a predetermined level, characterized in that said restraining means comprise a pin disposed on said contact end 10 portion, and a torsion spring having a free spring arm thereof resiliently engaged with said pin so as to normally urge the movable contact toward the contact-closed position, the location of said pin relative to the pivot axis of the associated contact being such that independent movement of the 15 movable contact in the contact-open position will cause the pin to ride on the free spring arm to a position enabling the latter to hold the contact in said contact-open position, and that subsequent movement of the cross-bar to said contact-open position will cause the pin to return upon said free spring 20 arm to its normal position. 6. An electric circuit breaker according to claim 5, characterized in that said torsion spring is mounted on a pin supported in sidewalls of the associated pocket-defining portion of the cross-bar. - 38 7. An electric circuit breaker according to any one of the preceding claims, characterized in that each contact pivotally supported on said cross-bar has connected thereto a flexible conductor forming part of a current-carrying path extending 5 through the circuit breaker, said flexible conductor extending into the associated pocket and being connected to said end portion of the associated contact at a location proximate to the pivotal axis of the cross-bar. 8. An electric circuit breaker substantially as hereinbefore 9. 10 described with reference to the accompanying drawings. Dated this 16th day of November 1984 Cruickshank & Co. Agents for the Applicants,