US2370054A - Circuit breaker - Google Patents

Description

Feb. 20, 1945. T'. .NDSTOM Em 2,310,054

CIRCUIT -BREAKER Filed OCL. 21, 1941 3 Sheets-Sheetl 1 www * Feb 20, 1945- T. LINDSTROM ET AL 2,370,054

CIRCUIT BREAKER Filed 0G12. 2l, 1941 3 Sheets-Sheet 2 Fell .20', 1945. T. LINDSTROM ET Al. 2,370,054

CIRCUIT BREAKER Filed Oct. 2l, 1941 3 Sheel'.S-Shee'tl 5 Il//llllll'llll lll v 2 160 v179 15a 173201205 2"? 235 v Patented Feb. 20, 1945 UNITED STATESl PATENT OFFICE CIRCUIT BREAKER Turc Lindstrom, Edgewood, and John W. May,

Pittsburgh, Pa.,

assignors to Westinghouse Electric & Manufacturing Company, East Pittsu burgh, Pa., a corporation of Pennsylvania Application October 21, 1941, Serial No. 415,912

(Cl. 20G-88) 9 claims.

it is an object of this invention to provide a" sing means of the trip lei-:ition to provide inproved rip vice provided rwith biasing ereirom under certain ions and .ha ci the biasing means conditions.

Another object of the invention to provide a circuit breaker having an improved trip device in which a latch ls provided for normaliy latching biasing means to a trip member, said latch being operable to disconnect the biasing means under certain abnormal circuit conditions and which is provided with another latch to prevent disconnection of the biasing means under certain other abnormal circuit conditions.

certain other A further object of the invention is to provide a circuit breaker with an improved trip mechanism wherein' a thermal element operates a latch which permits a trip member to automatically disconnect itself from a biasing means.

An object of the invention is the provision of a circuit breaker having an improved electromagnetically responsive and thermally responsive trip device which is operable to cause automatic opening of the breaker instantaneously upon the occurrence of overloads above a predetermined magnitude and after a time delay introduced by` a thermally responsive element in response to overloads below the predetermined magnitude.

Another object of the invention is the provision of a circuit breaker with an improved trip device having a current responsive electromagnetic means which is operable to cause automatic opening of the breaker, and a spring biased member releasably connected to a trip elementI operated by the electromagnetic means for normally cpposing operation of the trip element but which is caused to be released from the spring biased member by a thermally responsive element when the thermally responsive element is heated a predetermined amount in response to overload current. Another object of the invention is the provision of a circuit breaker having an improved trip` device as previously described and wherein the spring biased member which opposes operation of the trip element is releasably connected there.. to by an anti-friction latching means which reduces to a minimum the operating eiiort required or" the thermally responsive element to cause unf latc'ning of the trip element.

The present invention constitutes a further development and improvement over the invention disclosed claimed in the copending applica tion. John W. May, Seriali Nm 424,423., filed December 2b, i941, new Patent No. 2.357,21?, is sued Aug. 29, 194%, and assigned to the assignee oi thepresent invention.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings, in which:

Figure l is a vertical sectional view through the center pole of a three-pole circuit breaker ernbodying the features-of the invention.

Fig, 2 is a fragmentary horizontal sectional view at an enlarged scale taken substantially on line II-II of Fig. 1 and showing the trip mechanism for two ofthe poles.

Fig. 3 is a vertical sectional view through the trip device taken substantially on line IlI-III of Fig. 2, showing the trip member operated after it has been caused to be released from the spring biased member by operation of the thermally responsive element.

Fig. 4 is a vertical sectional view similar to Fig. 3 but showing the trip member in operated vposition Without having the biasing means disconnected therefrom.

Fig. 5 is a vertical sectional view similar to vice of the breaker. The parts are illustrated in their untripped positions.

Fig. 6 is a vertical sectional view similar to Fig. but showing the parts in the positions they assume after the bimetal element has caused the release of the trip lever from the spring biasing` means.

Referring to Fig. 1, the circuit breaker is of the multipole type and is provided with a common operating mechanism mounted on a main frame I1 (Fig. 1) secured to the center portion of a base H. The base is of insulating material and the main frame I'l is secured thereto by means of bolts 2l and 23. The frame I1 comprises a pair of spaced substantially parallel mem-'- bers rigidly joined adjacent the base i l by a cross member I9 and at the outer end by a cross member 25. A casing I3 (shown by dotted and dash lines) may be provided to enclose the circuit breaker. a

A contact arm 30 for the center pole of the breaker is provided with a pair of spaced arms 30 disposed one on each side of a connector 21 rigidly secured to the cross member I9 and to the base Il by the bolt 23. The arms 3| are pivotally supported on ashort shaft 29 extending through a suitable opening in the connector 21 and through bearing openings provided therefor in the sides of the frame I1.

The contact arm 30 pivotally carries a main contact member 41 supported on a pivot 49 mounted in spaced projections '5i (only one being shown) of the contact arm 39. A movable contact 33 secured to the contact member 41 cooperates with a stationary main contact 39 mounted on a conductor 4l which is secured to the base Il by means of bolts 43.

An arcing contact member 55 is pivoted on a pivot pin 51 supported in a pair of spaced projections 59 (only one being shown) on the con- .tact arm 30. The arcing contact member 55 has secured thereto an arcing contact shoe 95 cooperating with .a stationary arcing contact 377 which is secured to an arcing horn 36. The arcing horn 36 is secured to the conductor 4i by means of screws 38. The conductor 4l vis bent at right angles and projects through an opening in the base Il to form a terminal connector 45.

vContact pressure is provided for the main 'contacts 33-39 by means of a spring 53 compressed between avspri'ng seat on the contact arm 39 and a spring seat on the main contact member 41. In a similar manner the arcing contacts 35-31 are provided with spring pressure through the agency of a spring 63 surrounding a rod Si which ispivot-ally connected to the arcing contact member 55. The spring 63 is compressed between a washer `liti seated on a shoulder of the rod 6l and a spring seat on the contact arm 30. The rod 6l slidably projects through'an opening in the contact arm 30 and has a nut 15 screwed onto its outer end.

As previously stated, lthecircuit breaker is of the multipole type, and each ofthe poles of the circuit breaker has a stationary contact means and a movable contact means similar` to that of the center pole shown in Fig. l and described above, except that the contact arms of the outer poles do not have extending pivot arms corresponding to the arms 3l of the center pole contact arm 3U. Each of the three contact arms is securely clamped to a steel tie bar 61. by means of a clamp and a bolt 1|, as shown on the center pole contact arm 39, so that all of the rthree contact arms and the movable contacts carried thereby are operated simultaneously. The movable contacts of the poles are insulated from each other by a sheath of insulating material surrounding the tie bar and disposed between the tie bar 61 and the clamp portions of the contact arms.

When the contact arm 30 for the center pole is rotated in a clockwise direction (Fig. 1) to open the contacts, as will presently be described, the springs 53 and 63 rock the contact members 41 and 55, respectively, counterclockwise about their pivots. The counterclockwse movement of each main contact member 441 is limited by a projection 13 thereon striking the body of the contact arm 3B, and the counterclockwise movement of each arcing contact member 55 is limited by the nut 'I5 on the rod 6l striking the contact arm 3|). The adjustment of the nut 15 on the rod- 6i is such that the main contacts 33-39 open shortly before the arcing contacts 35-31 open.

lllhe arc resulting from the rupture of the current is drawn into an arc extinguisher 16 where it is broken up into a plurality of small arcs and these arcs quickly cooled and extinguished. The

arc extinguisher 16, of which there is one provided for each pole of the breaker, is of a well known type and comprises, generally, a stack of slotted plates disposed adjacent the path of travel of the arcing contact 35. The plates serve to draw the arc toward the ends of the slots where it is extinguished.

The electrical circuits for the several poles of the breaker are the same, the circuit of each pole extending from the terminal 45 through the conductor lid, the stationary main contact 39, the movable main contact 33, main contact member 41, a exible shunt conductor 19 connecting the main contact member 41 and the connector 2li, a connector l2 secured to the connector 21. by means of bolts 1li, a heating conductor 18 having its upper end secured to the connector 12 and its lower end connectedv to one end of a magnet coil 89, and through the magnet coil 89 to a terminal connector 93. The terminals 45 and 83 serve to connect the breaker in an electrical circuit.

The circuit for the arcing contacts extends from the conductor 4I through the arcing contacts 31 and' 35, the arcing contactv member 55, a iiexible shunt conductor 11 to the main contact member 4l' and thence over the previously de scribed circuit to the terminal 83.

The contact arm 30 for the center pole isbiased in a clockwise direction toward open position by a pair of springs 85, only one of which is shown. having one end connected to the contact arm 39 near its free end and the other end anchored on a fixed -pivot pin 81 supported in the main frame l1. Under normal circuit conditions the contact arm 39 is releasably restrained in its closed contact position (Fig. 1) by means of a toggle and linkage arrangement of the common operating mechanism which toggle and linkage is collapsible to cause opening of the contacts.

The mechanism linkage comprises a lever 89 pivotally mounted on a xed pivot 9| supported in the main frame l1, and this lever comprises a pair of levers rigidly joined by a cross member H1. The lever 89 is connected to the arms 3| of the center pole contact arm 30 by a. main operating toggle comprising a, toggle link 93 having one end pivoted on a pin IUI in the lever 89 and a toggle link 95 having one end pivoted on a pivot pin 99 in the arms 3l, the toggle links 93 and 95 aavaote .being pivotally connected by a knee pin Si. The link 85 comprises a pair of links rigidly joined by a cross bar H5. The free end of the lever 89 is connected by a link |03 to one arm of a lever |05 pivoted on the fixed pivot 8l. The other arm of the lever N5 is pivotally connected to a link |01 of a tripping toggle comprising the link |01 and a link |09 pivoted on a fixed pivot H3 mounted in the frame il, the toggle links Ill'l and |09 being pivotally connected by a knee pin lil. a pair oi links joined by a yoke il@ having a bent portion to which is secured an extension E26 ci insulating material. The toggle link it@ com prises a pair of links joined near the pivot H3 'by a yoke E23 having formed poitions M5 and E221' thereon. The lever it and the link il each comprises a pair of members jolned'bv a yoke substantially as illustrated. The extension lili on the yoke I |9 cooperates with a manually oper able handle IM to trip the breaker in a manner to be later described.

The linkage just described serves to releasably hold the Contact assemblage in closed contact position. When the contact arm t@ is in the closed contact position, the main operating toggle B-il is over-center `above a line through the centers oi the pins 99 and lill, and the toggle comprising the link 93 and B5 and the lever is over-center above a line through the center o the pin BS and the xed pivotA Si. The upward over-center movement of the main operating tog-z gie 93--95 is limited by the projecting end oi the link 93 engaging the cross bar M5. With the main operating toggle @J3- 9E and the toggle til-93 and B9 in their over-center positions the springs 85 bias the lever te in a clockwise direction. Movement of the lever 8S, however, is normally prevented by the tripping toggle lill-m9 which is biased over-center to the lef-t of a line drawn through the center of the fixed pivot H3 and the point of connection of the toggle link l'l andthe lever |05, by means of a spring |23 tensionefl ybetween the yoke H9 and the fixed pivot H3. The over-center position of the tripping toggle is adjustably determined by a screw |29 in the cross member 25. The tripping toggle icl-|08 in its over-center position, 'acting through the lever |05 and link H33, prevents clockwise rotation of the lever 3S and consequently holds the movable Contact assemblage in the closed contact position against the action of the springs B5.

The tripping toggle aaims is adapted to bev moved outwardly over-center toward collapsed position to cause opening of the contacts by a trip device, indicated generally by the reference numoral |33, acting through a trip rod E; trip rod |35 is slidable vertically through the coil of a shunt tripelectromagnet enclosed in a casing `|38 secured to the main frame il. The shunt The toggle link lill comprises The v of the previously mentioned operating handle lill toggle 93-95 does not immediately collapse, but moves as a unitary linkage transmitting the movement of the contact arm 3|] to rock the lever 89 ln a clockwise direction. This movement of the lever B9 is transmitted through the linkage lliE-lllto complete the collapse of the tripping toggle lill-lot.

The clockwise or opening movement oi the contact arm Sii is arrested byv projections (not shown) thereon Striking a portion lill of the main. frame il. At this time the inertia of the linkage starts the toggle @i--ll over-center in a direction to cause its collapse. By the time knee pin Si of the main toggle has passed below the line Fill-l1 l the Weight of the linkage and parts causes the main toggle 93-95 to collapse and causes the lever link. itil, lever M35 and tripping toggle iol--liit to be automatically .res i, to their normal positions as shown in Figl main operating toggle llt-Q5 remains in collapse condition until the contacts are closed. The contacts can be closed by manual operation.

The handle is rotatably mounted in a bracket i ci insulating material secured to the outer end o the main fran-le il.l A link itil connectedv a crank on the shaft oi" the handle is adapted. to be thrust downwardly (Fig. l) upon clockwise or closing movement of the operating handle ili. The link llii is notched at its lower end and engages an hourglass shaped roller lil@ rotatably mounted on a cross member lill? rigidly connecting the outer endroit a pair of levers Mb. The levers i535 straddle the frame il and are pivotally supported on the endsoi the fixed pivot on opposite sides or the frame il, and their inner ends are rigidly connected by cross bar it. The levers N5 and the cross bars lill and M9 form a contact closing lever pivoted at el, the levers M5 being spaced apart anddisposed one on each side of the frame lll. A pivot pin itil mounted in spaced projections it?. on the cross bar lll@ of the closing lever. rotatably supports a roller i155 which is adapted to engage the knee of the main operating toggle to move the toggle torextended position te close the breaker upon clockwise movement of the closing lever M5.

Rotation of the operating handle lili in a clockwise or closing direction, indicated by the arrow trip coil is adapted to be energized over a shunt circuit (not shown) or by a manually controlled switch to operate the trip rod |35'frorn a remote point in a manner well know-n in the art.

The trip device |33, when actuated in response to an overload current, thrusts the trip rod |35 upwardly, at which movement theupper end of the rod strikes the formed portion |21 of the toggle Alink |09 and rocks said toggle link clockwise about the xedipivot H3. The clockwise movement of the link |09 causes collapse of the tripping toggle lill-|09v which permits the springs 85 to lrock the contact assemblage clockwise to open the contacts. The main operating in Fig. l, thrusts the link ibi downwardly and, due to the cooperation of the notched lower end of the link with the roller H53, rocks the contact closing lever Altli in a clockwise direction. During this movement, the roller 55 carried by the closing lever engages the link 93 oi the now col lapsed main toggle .Q3- Sli and moves the toggle to its extended over-center position. Since, at this time, the tripping toggle itl-lill? is overcenter in its restraining position, the lever @Q is prevented from rotation, and consequently the force applied to straighten the toggle 93-95 rotates the contact arm 3Q in a counterclockwise direction to close the contacts and tension the springs 3E. The clockwise movement of the contact closing lever |45 and the roller |55 is suincient to carry the toggle @Si- 95 over-center above the line St-ll so that the contacts are held in. their closed position until the breaker is again tripped.

As soon as the contacts are closed and the toggle 93-95 is moved to its over-center position, the handle HH is released, lwhereupon a spring |59 tensioned between a projection on the frame I1 and the contact closing lever M5 rocks the lever counterclockwise, thrusting the link 45| upwardly and restoring the handle |4| to its neutral position (Fig. 1). The counterclockwise movement of the closing lever |45 is limited by the cross bar |49 striking the casing |38 of the shunt trip electromagnet.

The contact closing lever |45 may be operated to close the contacts automatically through the agency of a motor |39`mounted lon a 'supporting plate of insulating material secured to the frame l1. The motor |39 may be energized from any suitable source and in a manner well known in the art. When energized the motor is adapted, through the medium of suitable driving connection, to rotate a crank disk |30 which carries an antifriction roller |3|. An arm |34 secured to the side of the contact closing lever is provided with a cam face |32 normally disposed in the path of rotation of the roller |3l.

When the disk |30 is rotated, upon energization of the motor |39, the antifriction roller engages the cam face |32 and rotates the arm |34 and the contact closing lever |45 in a clockwise direction to straighten the toggle 93-95 and close the contacts in the manner previously described, As soon as the roller |3| passes out of engagement with the arm |34, the spring |59 acts to restore the closing lever |45 to its normal position. The motor |39 is deenergized by a suitable limit switch (not shown).

The circuit breaker may be tripped manually by rotating the handle |4'I through a small angle in a counterclockwise direction from its neutral position. Rotation of the handle in tripping direction causes a projection (not shown) on the link |5| to engage the previously described extension |2| on the `yoke |9 of the toggle link |01, and move the tripping toggle |01|09 overcenter in a direction to cause its collapse. This permits the springs 85 to open the contacts in the previously described manner.

The trip device indicated generally at 33 (Figs. 1, 3 and 4) is operable to actuate the trip rod |35 after a time delay on overloads below a predetermined value, for example, approximately 1000% of normal rated current, and instantaneously on overloads above said predetermined value.

Referring to Figs. 2, 3 and 4, each pole of the trip device is of the same construction and comprises a laminated magnet core |6| secured by screw bolts |69 to a plate |1| of insulating material which is securelymounted on the base by bolts |10. The magnet core 8| is U-shaped, at least as to a part of the laminations which extend transversely as at 82 and are surrounded by the coil 80 connected in series relation with the heater conductor 18 in the circuit of the breaker. Those laminations extending through the coil 80 are surrounded by an insulating tube 84 provided with end flanges 86 also of insulating material.

One end of the coil 80 is electrically secured to a connector 88 to which is also secured the lower end of heater conductor 1,8. The other end of the coil 80 is secured to the terminal connector 83 by a screw 92, the terminal 83 being securell7 mounted on the insulating plate |1| by means of screws |12. The lower end of the heater conductor 18 is secured to the connector yB8 by a screw 98 and the connector is secured to a block 94 of insulating material by a'screw 98.

The trip mechanism of each pole is supported in a frame comprising a pair of spaced substantially parallel plates |63 rigidly connected at their outer ends by a substantially horizontal cross member |65. 'I'he plates |63 have mounting feet |l61 formed thereon through which the bolts |69 and |10 pass to rigidly secure the frame |63 to the magnet structure, the entire trip device being thus rigidly supported on the base I|.

A trip lever |13 comprising a pair of parallel levers connected at their outer ends by a cross member |11, is pivotally supported on a rod |15 mounted in the frame |63. The trip lever |13 carries an armature |19 comprising a pair of laminated armatures each securely riveted to one of the levers |13 and joined by armature frames (Figs. 2, 3 and 4).

An adjusting screw |8| secured in the cross member |11 by means of a lock nut |83 is adapted to cooperate with an arm mounted on a trip bar |81. The trip bar is rotatably supported in a bracket |89 on the casing |38 of the shunt trip electromagnet, and extends across all of the poles of the breaker. There is .an armA |85 provided on the trip bar |81 for each pole and the center one of said arms is in line with the trip rod |35 and. as previously stated, is adapted upon operation of the trip bar by the trip device |33 for any one of the poles, to thrust the rod |35 upwardly to trip the breaker.

The trip lever |13 is normally biased against operation by the magnet core |6| by a pair of springs |9| but is adapted to be disconnected from the springs by a thermally responsive bimetal element |93 when the bimetal is heated a predetermined amount due to an Joverlo-ad cur'- rent belowthe previously mentioned predetermined value. The bimetal element |93 is secured by means of rivets to a looped portion of the heater conductor 18 and the heater conductor is on a rod |96 mounted in spaced brackets |91 depending from the cross member |65 of the frame |63. The upper ends of the spring |9| are anchored on the ends of a rod |99 carried in the ends of a pair of spaced parallel arms 20| pivoted on the rod |15. The arms 20| are joined by an integral yoke 203. A spring 205 has one end connected to the yoke 203 and its other end con-- nected to a pin 201 carried by the trip lever arms |13. This spring 205 serves to bias the trip lever 13 and armature |14 to normal unattracted position with a predetermined force independently of the springs |9| i. e. even though the trip lever is released from the springs |9 The rigidly connected arms 20| and conselquently the springs |9l are normally connected to the trip lever |13 by an antifriction latch 209 pivotally supported on the rod |99 and having a recess 2|I therein normally embracing a latch roller 2|3 rotatably supported on a rod 2|5 supported in the trip lever |13.

lAttraction of the armature |19 by the magnet core |6|, when energized, tends to rotate the trip lever |13 in a counterclockwise direction. This force is applied through the roller 2 |-3 to. the latch 209 in a direction to rotate the latch in unlatchingl or counterclockwise direction. This is normally prevented by a latch arm 2 1 pivoted on a rod 2| 9 carried between the arms 20| and biased in latching direction by a spring 22|. The lower cnd cf the latch arm 2|1 is provided with a latch shoulder 223 releasably engaging a roller 224 rotatable gllga pin 225 carried by the tail ;221 of'the latch in this position the latch 209 is held in position to restrain the trip lever |13 including the armature |19 in unattracted position.

When the bimetal |93 is heated a predetermined amount it exes upwardly engaging the insulating element 23| and rocks the lever 259 counterclockwise about the pivot 2 I9. This moves the pivot pin 26| to the right of the center line 2 I 9-225. The overload current which heats the bimetal |93 and causes it to flex also increases the energization of the electromagnet |6I. This increases the pull of the magneten the trip lever |13 which is applied in an upwardly direction to the latch 209 through the agency of the latch roller 2|3. Since the toggle 251-259 is now over center to the right of the line 2|9-225 the pull of the magnet rocks the latch 209 counterclock- Wise to release the trip lever |13 from the springs |9| and cause tripping of the breaker. This counterclockwise movement of the latch 209 rocks the link 251 counterclockwise about the pivot 26| and causes the lever 259 also to rotate in a counterclockwise direction about its pivot 2|9 against the tension of the spring22l. The counterclockwise movement of the latch 209, the link 251 and the lever 259 is limited by a yoke portion 266 of the link 251 striking a shoulder 261 on the arm 259. The parts are shown in their operated positions in Fig. 6.V y

As soon as the electromagnet |6| is deenergized the spring 205 rocks the trip lever |13 clockwise to its unattracted position. Near the end of the clockwise travel of the lever |13 the latch roller 2|3 strikes the shoulder 2 I4 of the latch 209 and rocks said latch clockwise toward latching position. The latch 209 however, does not resume its full latching position until the bimetal |93 l has cooled and assumed its normal position. As the bimetal cools it permits the spring 22|, aided by the spring 205 through the agency of the roller 2|3, to rock the arm 259 clockwise to its normal position (Fig. 5). This movement straightens the toggle 251- 259 and restores the latch 209 to its full latching position.

The front or right hand portion of the trip device is eectively insulated from the current carrying parts to prevent accidental contact with live parts, While the breaker is being adjusted. Reference to Figs. 3, 4, 5 and 6 discloses that the support bar |94 for the heater element 18 is insulated from. the heater element thus insulating the frame |63 from the heater element. The member 23| and the adjusting lever 239, both of insulating material, insulates the latch mechanism from the bimetal element.

From the foregoing description it can be seen that the effort required of the bimetal element to operate the latch mechanism and cause tripping of the breaker has been reduced to a minimum. In fact the only force the bimetal has to overcome to effect tripping of the breaker is the tension of the comparatively weak spring 22|. It can be further seen that the toggle and linkage structure of the operating mechanism (Fig. 1) greatly reduces the effort required of the trip device |33 to trip the breaker. The elimination or reduction of latch points and the provision of' load-reducing` devices permits the use of lighter parts and makes possible much faster operation of boththe trip device and the operating mechanism, and, in addition, materially reduces the cost of manufacture.

Having described the several embodiments of the invention in accordance with the patent tacts, operating mechanism for said contacts in-` cluding an operating handle, a trip device comprising a trip lever pivoted intermediate its ends and operable to cause an opening operation of said contacts irrespective of the position of said handle, an electromagnet operable in response to predetermined circuit conditions to actuate the trip lever, a member pivoted coaxially with said trip lever, means biasing said member against operation, a' latch mounted on said member for releasably connecting the member and the biasing means to the trip lever, a second latch mounted on said member normally restraining said rst named latch in latching position, and a bimetal element operable in response to predetermined circuit conditions for actuating the second named latch to cause disconnection of the trip lever from the spring biased member.

2. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member, a trip device operable to cause an opening operation of said switch member, said trip device comprising a trip member, biasing means for opposing operation of the trip member, means releasably connecting the trip member to said biasing means, a latch for latching the connecting means in connecting position, and a bimetal element operable when heated a predetermined amount in response to overload currents below a predetermined value to operate said latch to a non-latching position, said electromagnet being operable in response to overload currents below said predetermined value to then move said connecting means to a disconnecting position, said electromagnet being operable in response to overload currents above said predetermined value to operate the trip member without disconnecting the biasing means.

3. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member including an operating handle, a trip device comprising a trip member pivoted intermediate its ends and movable to cause an opening operation of said switch member irrespective of the position of said operating handle,

an electromagnet responsive to overload currents for operating said trip member, a pivoted arm, biasing means attached to said arm, a member pivoted on said arm for connecting and disconnecting the biasing means and the trip member, a latch pivotally supported on said arm and-operable to cause disconnection of said trip member from the biasing means, a thermally responsive means operable in response to overload currents for operating the latch, and a spring conn ected at one end to the trip .member and at its other end to the pivoted arm for biasing the trip member to unoperated position at least when the biasing means is disconnected therefrom,

4. In a circuit breaker, relatively movable contacts, operating mechanism including a linkage operable to cause opening of said contacts, a trip device comprising a trip lever operable to actuate said linkage, an electromagnet operable in response to overloads to operate the trip lever,

means biasing the trip lever against operation. a latch normally 'connecting said biasing means to said trip lever, said latch being operable to unlatching position by the force exerted thereonA by said electromagnet to disconnect the biasing means, a. second latch normally preventing unlatching movement of said rst named latch, a bimetal element operableuin response to overload currents below a predetermined value for moving the second named latch to unlatch the ilrst named latch to permit said electromagnet to disconnect said biasing means, and said electromagnet opl erating said trip lever to tripping position against the force of said biasing means to instantaneously trip the breaker in response to overload currents above said predetermined value.

5. In a circuit breaker, relatively movable contacts, operating mechanism for said contacts including-an operating handle, a trip device including a trip member operable to cause an opening operation of the contacts irrespective of the position of said handle, an electromagnet responsive to predetermined circuit conditions for actuating the trip member, spring biasing means oposing operation oi.' the trip member, means releasably connecting the biasing means to the trip ymember, said connecting means being operable to disconnecting position by the torce of saidrelectromagnet, to release the trip member from the biasing means, means for positively restraining the connecting means in connecting position, and a thermally responsive element operable when heated a. predetermined amount in response to overload currents below a predetermined value to move the restraining means. to a position wherein it is ineiective to restrain the connecting means in connecting position to thereby permit said electromagnet to move said' disconnecting means to disconnecting position, and said electromagnet operating said trip member without disconnecting the biasing means to instantaneously trip the breaker in response to overloads above said predetermined value.

6. In a circuit breaker, relatively movable contacts, operating mechanism for said contacts, a trip device, including a trip member operable w cause an opening operation of the contacts, an electromagnet responsive to predetermined circuit conditions to,actuate the trip member, biasing means comprising a spring opposing operation of the trip member, means releasably connecting the biasing means to the trip member. said means being operable to release the trip member from the biasing means, 'a toggle releasably restraining the connecting means in connecting position, and a bimetal element heated in 7. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member, a trip device comprising a trip member pivoted intermediate its ends and operable to cause an opening operation of the operating mechanism, electromagnetic means for operating the `trip member in response to overload currents, biasing means comprising a spring opposing operation of the trip member, a latch normally connecting said biasing means to the trip member, a toggle normally restraining said latch in latching position, said toggle being operable under. certain circuit conditions to cause disconnection of the Vtrip member from the biasing means, and current responsive thermal means operable in response to predetermined circuit .conditions to operate said toggle, said biasing means remaining connected to said trip member when said member is operated in response to overloads above a predetermined value.

8. In a circuit breaker,`relatively movable contacts, operating mechanism for said contacts, a

trip device including a trip member operable to cause opening of the contacts, biasing means comprising a spring normally oposing voperation `oi. the trip member, means comprising a latch for releasably connecting thev biasing means to the trip member, a toggle connected to said latch response to overload currents and operable when for normally restraining said latch in latching position, said toggle being and operable to cause disconnection of the trip member from the biasing means, and a bimetal element operable when heated a predetermined amount in response to overloads below a predetermined amount for operating the toggle,said bimetal'element constituting the sole means for eiIecting disconnection ofv the trip member from the biasing means.

9. In a circuit breaker, relatively movable contacts, operating mechanism for said contacts, a trip device comprising a pivoted trip lever operable to cause an opening operation of said contacts, an electromagnet operable in response to overload currents to operate said trip lever, a member pivoted coaxially with said trip lever, means comprising a spring biasing said member against operation, -a latch memberpivotally supported by said member for connecting said member to the trip lever, means supported by said member biased to a position for restraining said latch in latching position, a bimetal element operable in response to predetermined overload conditions to operate said restraining means to a non-restraining position to effect disconnection of theA biasing means from the trip lever, and means for adjusting the operating characteristics of said bimetal element.

TURE LINDSTROM. JOHN W. MAY.

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