US2586429A - Circuit breaker operating mechanism - Google Patents

Description

Feb. 19, 1952 J. K. HODNETTE ET AL CIRCUIT BREAKER OPERATING MECHANISM 2 SHEETS-SHEET l Filed July 5, 1947 .m um

INVENTORS .Zahn A. Hadnve and WITNESSES:

Feb 19, 1952 J. K. HoDNl-:TTE ET A1.

CIRCUIT BREAKER OPERATING MECHANISM Filed July 5, 1947 2 SHEETS--SHEET 2 WITNESSES:

ATTORN Patented Feb. 19, 1952 CIRCUIT BREAKER OPERATING MEoHANIsM John K. Hodnette and Merrill G. Leonard, Sharon, Pa., assignors to Westinghouse Electric Corporation, East Pitt tion of Pennsylvania sburgh, Pa., a corpora- Application July 5, 1947, Serial No. 759,272 Claims. (Cl. 20G-116) This invention relates to circuit breakers, and more particularly, to operating and tripping mechanism therefor.

Certain features disclosed but not claimed in this application are fully disclosed and claimed in copending divisional applications, Serial No. 240,875 and Serial No. 240,876, filed August 8, 1951, by John K. Hodnette and Merrill G. Leonard, and assigned to the assignee of this application.

One object of the invention is to provide a circuit breaker embodying an improved operating mechanism wherein the load of the main operating spring is not imposed on the breaker latch.

Another object' of the invention is to provide a circuit breaker embodying a trip member controlled by a thermal trip element to trip the 'breaker and to effect an indication of the condition of the breaker, and an indicating trip member controlled by said thermal trip element to effect an indication of the approach of a dangerous circuit condition.

Another object of the invention is to provide a circuit breaker embodying a; trip member controlled by a thermalA trip element to trip the breaker and to eiiect an indication of the condition of the breaker, an indicating trip member controlled by said thermal trip element to effect an indication of the approach of a dangerous circuit condition and means operatively relating the operating mechanism of the breaker andy the indicating trip member to permit resettingV of said indicating trip member without disturbing the breaker contact position.

Another object of the invention is to provide a circuit breaker embodying a thermal trip device responsive to overload current to trip the breaker and an auxiliary thermal element responsive to ambient temperatures to control the thermal trip device to trip the breaker after a relatively long time delay when the ambient temperature is low and after a relatively short time delay when the ambient temperature is high.

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 best be understood from the following detailed description thereof when read in conjunction with the accompanying drawings.

In said drawings:

Figure l is an elevational sectional view taken along line I-I of Fig. 2 showing a circuit breaker be more fully described hereinafter.

2 embodying the principles of the invention, the breaker being shown in the closed position,

Fig. 2 is a sectional view taken on line II--II of Fig. l and looking in the direction of the arrows,

Fig. 3 is an elevational view similar to Fig. 1 but showing the breaker in the tripped open position, and

Fig. 4 is an elevational view similar to Fig. 1 but showing the parts in the reset position.

Referring to Fig. l of the drawings, the circuit breaker comprises a base I'I of insulating material on which is mounted the breaker contact structure, a metal housing I3 secured to the base II, an operating mechanism indicated generally at I 5 and a trip device indicated generally at I1.

The contact structure comprises a main stationary contact I9 rigidly mounted on the inner end of a rod 2I slidably mounted in the base II. A coil spring 23 surrounds the rod 2| and is compressed between the base II and a connector 25 secured to the rod 2I and to the contact I9 to provide contact pressure. A limit nut 21 .is threadedly mounted on the rod 2I outside the base II. A cooperating movable contact 2i is rigidly mounted on a channel-shaped switch arm 3| pivotally mounted on a p-ivot pin 33 supported in a U-shaped bracket 35. The bracket is secured to the base II by means of a screw 3l.

The contact structure also comprises a stationary arcing contact 39 rigidly mounted on a conducting support member 4I' secured by means of a screw 43 to the base II. and a cooperating movable arcing contact 45. The movable arcing contact 45 is rigidly mounted on a channelshaped switch member 41 which stra'idles the switch arm 3I and is pivoted on the pivot pin 33. A compression spring 49 disposed between an extension 5I of the main switch arm 3I and the yoke portion 53 of the arcing Contact switch arm 41 provides contact pressure for the arcing contacts 39-45 and also maintains the arcing contacts in closed position until after the main contacts I9-29 have separated on an opening operation.

The operating mechanism I5 is supported in a generally U-shaped frame 55 the bight 57 of which is rigidly secured to the housing I3. The operating mechanism comprises a releasable member or carrier 59 pivotally mounted on a xed pivot pin 6I mounted in the side members of the frameV 55. The carrier 59 has a latch portion 63 adapted to engage alatch member 65 forming part of the trip mechanism which will The carrier 59 is biased in a clockwise direction by means of a spring 61 which surrounds a. spring guide 69 pivotally connected at one end by means of a pivot pin 1| to the carrier. The spring 61 is compressed between a shoulder on the spring guide 69 and a rod 13 mounted on and extending between the side members of the frame 55. The carrier 59 is operatively connected to the switch arm 3|y by means of a toggle comprising toggleA jects beyond the side members of the switch arm 3| and through elongated slots 05 (only one being shown) in the side members of the arcing contact switch arm 41. v

An actuator comprising a pair of spaced actuating levers 91 is provided for operating the toggle 15-11 to manually open and close the contacts. The actuating levers 91 are disposed adjacent the inner sides of the U-shaped frame 55 and each of the levers carries a pivot pin 89 which is seated in a slot 9| in the adjacent frame. The actuating levers 01 are rigidly joined by an integral cross member 93 and each of the levers 81 is provided with a hook portion 95 which in the closed position of the mechanism engages an end of the knee pivot pin 19 to hold the toggle 15-11 in a slightly underset position to thereby hold the switch arms 3| and 41 in the closed contact position.

A pair of overcenter springs 91 is provided to operate the levers 81 and therethrough the toggle if 1511 in order to manually open and close the circuit breaker. The springs 91 have one end hooked over laterally projecting ears 99 on the levers 81 and the other ends of the springs are hooked over an operating rod extending through guide slots |03 disposed in parallel alignment in the frame members 55. Secured to a shaft for rotation therewith is a pair of operating arms |01 each having its free end bifurcated to embrace the rod |0| adjacent the ends thereof. The shaft |09 is pivotally supported in plates |09 secured to the outside of the housing I3 and provided with mounting feet I I whereby the circuit breaker may be mounted on a suitable support (not shown). One end-of the shaft |05 extends to the outside of the housing and has secured thereto an operating handle indicated at ||3 (Fig. 2) for manually operating the shaft |05 and the arms |01.

The circuit breaker may be opened manually by rotating the handle ||3 and consequently the shaft |05 and arms |01 approximately 90 in a counter-clockwise direction from the position shown in Fig. 1. During this movement the arms |01 cause the rod |9| to move upwardly in the slots |03 carrying therewith the vends of the springs 91 attached thereto. When the rod |05 moves the line of action of the springs |01 overcenter above the pivot 89 of the levers 81, they bias the actuator levers 81 in a clockwise direction. Continued movement o'f the arms |01 and the rod |9| increases the biasing force until a point is reached when the's'prings rotate the actuating levers 81 clockwise about the pivots 89. In 'the closed and latched position of the'circuit breaker, the pivot 83 connecting the toggle link 11 to the releasable carrier 59 is in axial alignment with the pivot 89 of the actuating lever 81 and the knee pivot pin 19 remains in engagement with the hook 95, consequently, the toggle link 11 and the lever 81 will move as a unit during manual opening operation. The clockwise movement of the actuator lever 31, therefore, causes collapse of the toggle 15--11 and opening of the contacts. During the opening movement of the mechanism the switch arm 3| is nrst moved in a counterclockwise or opening direction to open the main contacts lil-29 while the spring 49 maintains the arcing contacts 39-45 closed until after the main contacts have separated. Shortly after the main contacts have separated, the pin 8| engages the outer end of the slot 85 in the switch arm 41 and thereafter moves both switch arms 3|-41 to the full open position in unison in which position the parts are shown in Fig. 4. f

The contacts are closed by rotating the shaft |05 and the arms |01 clockwise from the Fig. 4 position to the position in which they appear in Fig. 1. During this movement the arms |01 carry the rod |0| therewith moving the line of action of the springs 91 over center below the aligned pivots 83-89, whereupon the springs 91 bias the actuating lever 81 in a counterclockwise direction, and, since the knee pin 19 of the toggle 15-11 is in engagement with the hook 95, the toggle is biased toits underset position. Continued clockwise movement of the arms |01 increases the spring bias on the actuating lever 81 and the toggle until a point is reached where the springs 91 suddenly straightens the toggle 1511 and closes the contact with a snap action.

The configuration of the slot |03 is substantial-r ly concentric with the ears 99 on the actuating levers 81 so the slot controls the springs 91 so as to produce as little change as possible in. the length of the over center springs 91 until the toggle is broken, thereby reducing the energy required to operate the breaker. As will be more fully brought out later, the shape of the slots |03 also control the operation of a reset lever.

The circuit breaker may be tripped open automatically by operation of the trip device l1 in response to overload currents. The trip device comprises a base ||5 of insulating material secured to the housing I3, a cover ||1 also of insulating material secured to the base ||5 by means of rivets ||9 (only one being shown), a biased member |2| releasable t0 actuate the latch 55 and a tripping bimetal element |23 which is operable to release the member |2 l. The bimetal element is secured at one end to a metal bracket |24 supported on insulating plate |25 mounted on the base ||5 and at the other end carries an insulating block |21 to which is secured a metal latch |29. A connector |3| is electrically connected to the free end of then bimetal element and a iiexible terminal conductor |33 is connected to the connector. The nexible conductor |33 extends to the left and is supported on a bracket |35 mounted on the base ||5. Thereafter the conductor |33 extends out through an opening in the cover ||1 where it serves to connect the breaker in an electrical circuit.` The bracket'l24,` and hence, the iixed end of the bimetal element is connected by means of a ilexible conductor |31 to the switch arms 3| and 41, the conductor |31 extending downwardly through an opening in the base where it is mechanically and electrically secured to a connector |39, and to the switch arms 3| and 41. The connector |39 provides a point where a terminal strip |40 may be connected to provide a third terminal between the bimetal and the controls. The main stationary contact I9 is connected by means of a flexible conductor l4| to the stationary arcing contact 39 and the circuit through the breaker is completed by means of a flexible terminal conductor |43 also connected to the fixed arcing contact 39 and extending out through an opening in the base l. An auxiliary bimetal element |45, disposed above the tripping bimetal |23 but insulated therefrom by a strip |41 of insulating material, is Xedly mounted at its left-hand end and adapted to deflect, when heated, in the same direction as the tripping bimetal |23.

The releasable member |2| is pivotally mounted at 49 on an adjusting arm i5! which, in turn, is pivotally mounted on a pivot pin |53 which is supported in a suitable opening in the base ||5. The pivot |49, adjusting cam |5| and pivot pin |53 are directly behind pivot |89, a second adjusting cam |9|, and pivot pin |43, as hereinafter described. The member |2| is biased by means of a spring |55 in a clockwise or tripping direction. The spring |55 has one end hooked into an opening in the member |2| and the other end anchored to the free end of the adjusting arms |5|. Secured to the adjusting arm 15| at a point adjacent its free end is a rod |51 (Fig. 2) which extends upwardly through an enlarged opening in the base t5 and has its upper end threaded to receive an adjusting nut |59. A spring |6| coiled about the rod |51 and compressed between the bottom surface of the base ||5 and a washer |53 biases the free end of the arm |5| downwardly. By turning the nut |59 in one direction the rod |51 may be moved upwardly rotating the arm |5| in a counterclockwise direction. Turning the nut |59 in the opposite direction permits the spring |9| to lower the rod |51 and rotate the arm |5| in a clock,- wise direction. Since the releasable member |2| is pivotally supported at |49 on the arm |5!, it

will be thus moved up or down relative to the latch |29 to thereby vary the overlap of the member |2| with the latch.

The latch member 65 is U-shaped and the two legs thereof are mounted on a shaft |55 for movement therewith, the shaft |95 being mounted for rotation in openings in the side members of the frame 55, The yoke portion |61 of the latch member is shaped inwardly to form a latch portion |99 which engages the latch portion 63 of the carrier 59 to normally restrain the latter in the position shown in Fig. l.

The bimetal element |23 has its high-expansion side facingI downwardly so that, when heated a predetermined amount in response tc overload currents, the bimetal element |23 will deflect upwardly to disengage the latch |29 from the releasable member |2|. When this occurs, the spring |55 rotates the member 2| clockwise about its pivot |49 and the lower end |1| thereof strikes the latch member 65 a blow to disengage the latch portion |69 thereof from the latch portion 63 of the carrier 59 thereby releasing the carrier. Upon release of the carrier 59, the spring S1 rotates the carrier in a clockwise direction about its pivot 5| to the position in which it appears in Fig. 3, thus moving the switch members 3| and 41 to the open -position. During the early portion of this movement the knee pin 19 of the toggle 15-19 moves out of the hook portion 95 of the actuator levers 81 and shortly thereafter the end of the spring 'P guide 69 strikes the toggle link 11. This action causes collapse of the toggle and rotates the toggle link 11 clockwise about its pivot 83 to eifect movement of the switch arms SI-A'i to the open position. The mechanism is shown in Fig. 3 in the tripped open position.

During the automatic opening operation, the knee pivot pin 19, as previously set forth, escapes from the actuating levers 81 and before the breaker can be reclosed it is necessary to reengage the actuating levers with the knee pin 19 and also to reset and relatch the carrier 59. Both of these operations are accomplished by moving the rod |0| upwardly in the slots |03 from the Fig. 3 position to the position shown in Fig. 4. This is done byV rotating the shaft |05 and the arms |01 in a, counterclockwise direction as far as they will go, the movement of the rod being limited by engagement with the upper end of the slot |03. During this movement the rod |0| carries the line of action of the springs 91 over center above the pivot 89 (Fig. 3) of the levers 81 whereupon the springs 91 actuate the levers in a clockwise direction until they engage the knee pin 19. Next in its upward travel, the rod I0| engages a projection |13 on the carrier 59 and rotates the carrier counterclockwise about its pivot 6 Near the end of this movement of the carrier 59 the latching end thereof Wipes by the latch portion |69 of the latch member which is then restored clockwise to latching position by means ,of a spring |15, the clockwise movement of the latch 65 being limited by engagement with the frame 55. During the counterclockwise movement of the carrier 59 the pivot 83 for the toggle link 11 moves back slightly beyond the normal position in which it is aligned with the pivot 89 of the levers 81. This movement thrusts the knee pin 19 into the hook portion of the levers 81, and provides a slight overthrow for the latching portion 63 of the carrier beyond latched position.

The rod |0| in its upward travel, next engages a cam surface |11 in one wall of a slot |19 in a resetting lever |8| which is pivotally mounted on the pivot pin 6 I, and in cooperation with the slots |03, moves this lever counterclockwise about its pivot. During this movement, an ear 93 (Figs. 2 and 4) formed at right angles to the upper end of the resetting lever engages the releasable tripping member |2| and rotates it counterclockwise past its latched position as shown in Fig. 4. The parts are now in the reset position as shown in Fig. 4, in readiness for a contact closing operation which is effected in the previously described manner by movement of the arms |01 and the rod |0| in a clockwise direction to the Fig, 1 posit-ion, during which movement the actuating levers 81 acting through the knee pin 19 straightens the toggle 15-11 and moves the switch arms to their closed positions. As the rod |0| nears the lower end of its movement, it engages a portion of the slot |19 in the resetting lever I 8| and restores this lever to its initial position, as shown in Fig. l.

The circuit breaker is designed for use in an oi1 insulated transformer, and it is the purpose of the auxiliary bimetal element |45 to modify the tripping time of the current-carrying tripping bimetal element |23 in accordance with the temperature ofv the surrounding medium. The bimetal element |45 is similar to the tripping bimetal |23 and 'also has its high-expansion side facing downwardly,Y hence, when heated, will defleet in the same direction as the tripping bimetal |23.

If the transformer temperature rises gradually so that the mass of copper, oil insulation, etc., tend to reach their maximum safe temperatures,

vthe auxiliary bimetaI |45, Which is heated by the oil temperature rise and to some extent by conduction and convection from the tripping bimetal |23, will deiiect in the same direction and at approximately the same rate as the tripping bimetal |23 which is heated by both current flow and oil temperature rise, hence the bimetal |45 will not appreciably change the trip-time curve of the tripping bimetal |23. If the transformer temperature is low andheavy overload occurs, the tripping bimetal |23 will be' heated rapidly, whereas the temperature of the auxiliary bimetal |45 will rise very little and will, therefore, exert a restraining force on the tripping bimetalI23. It will be seen, therefore, that for a given value of overload current, the circuit breaker will be tripped open after a relatively short time delay when the transformer temperature is high and after a relatively long time delay when the transformer temperature is low. By use of the auxiliary bimetal |45 heavier overloads may be carried for a short time without tripping, and the'greater temperature rise required to trip on such overloads will give faster cooling and thereby the time for resetting is reduced.

The trip-time curve of the trip device may be varied by substituting bimetal elements having different characteristics for the auxiliary bimetal element, by varying the space between the tripping bimetal and the auxiliary bimetal and by varying the thermal insulation between and around the bimetal elements and also by varying the characteristics of the tripping bimetal.

Means is provided for indicating a partial overload condition which is not of sufficient magnitude to trip the breaker open but which indicates that the current in the circuit is approaching a dangerous overload condition or that a dangerous overload condition has been approached and then cleared itself without tripping thebreaker, also to indicate that the breaker has been tripped open in response to a dangerous overload condition.

The indicating mechanism comprises a releasable member |81 (Figs. 1 and 2) pivotally supi ported by means of a pivot pin |89 on an adjusting lever |9|. The lever |9| is pivotally mounted on the pivot pin |53 which supports the lever on the base ||5 of the trip device. A spring |95 having one end hooked in an opening in one arm of the releasable member |81 and the other end hooked in an opening in the lever |9| biases the member |81 in a clockwise direction about its pivot |49. The member |81 is normally restrained against clockwise movement by engagement with the latch |29. An adjusting rod |91 (Fig. l), similar to the rod |51 (Fig. 2) for the lever |5I, is secured to the lever |9| at a point near its free end and extends upwardly through 'an opening in the base ||5. The upper end of the rod |91 is threaded to receive an adjusting nut |99 and a compression spring 20| coiled about the rod |91 is disposed between the base ||5 and a washer 203 bearing against the lever |0|. By this means the lever [9| can be moved up and down about its pivot |93 to thereby shift the pivot |89 for the member |81 and vary the amount of overlap between the member |81 and the latch |29. rThe member |81 is adjusted to be released by the latch |29 before the bimetal element |23 deflects far enough to release the member |2| to trip the breaker. The releasable member |81 is electrically connected by means of a .nexible conductor 205 to a conductor 201 extending transversely through the breaker and secured to the base |I5 of the trip device. The member |81 is made of conducting material and carries a stud or contact 209 also of conducting material which, upon release and clockwise movement of the member |81 is adapted to make butt engagement with the end of a fixed contact 2|| to thereby close an electrical circuit and energize an indication device (not shown) but preferably a signal light to give visual indication.

The releasable trip member |2| is also electrically connected by means of a exible conductor 2|3 to the conductor 201 and carries a contact 2|5 which, upon release of the member to effect tripping of the breaker, engages the end of a xed contact 2 |1 directly behind the xed contact 2|| and closes an electrical circuit to energize an indicating device. The fixed contacts 2| and 2|1 may be connected together and connected in a circuit (not shown) to energize a single indicator or they may be connected in separate circuits to energize separate indicators. The return circuit (not shown) from the indicators is connected to a supply conductor 2|9 also secured to the base ||5 but insulated from the supply circuit 201. The supply conductors 201 and 2|9 extend outside of the housing I3 (Fig. 2) to be connected to a supply circuit, or to be connected to similar conductors in another circuit breaker assembled adjacent the first breaker in a manner to be more fully described later.

As previously stated, the releasable signal member |81 is adjusted by means of the lever I9| and the adjusting rod |91 (Figs. 1 and 2) to trip and close the circuit to the indicator before the releasable trip member |2| is released to trip the breaker. Hence, if an overload current occurs which approaches a dangerous value and trips the signal member |81, but which is cleared before it releases the trip member |2 I, the member |81 will close its circuit and energize the indicating means. Under this circumstance, it is desirable to reset the member |81 Without opening or otherwise disturbing the main breaker contacts. This is accomplished by a partial stroke of the arms |01 and the rod 10| in opening direction which is elfected by a partial opening stroke of the handle ||3 (Fig. 2). During this partial stroke, the rod |0| engages the cam portion |85 of the resetting member |8| and rotates this member in a clockwise direction from its Fig. l position causing an ear 22| on the member |8| to engage an arm 223 on the member |81 to rock the latter in a counterclockwise or resetting direction to its relatched position as shown in Fig. l. After the release signal member |81 is relatched, the arms |01 and the rod |0| are restored clockwise to their normal positions and since the rod |0| was not moved far enough to carry the springs 91 over center, the main contacts remain in their closed position. If a single indicating device is utilized which is energized by both the releasable member |2| and |81 with their contacts electrically connected in parallel, and this indicator remains energized after the member |81 has been reset, it indicates that the breaker has been tripped open and must be reset and reclosed. However, with two indicators operated independently by the member |81 and the trip member |2I, a single energized indicator would inform the attendant that an overload had occurred but had cleared without tripping the breaker, in which event it would only be necessary to reset the member |81 without opening the breaker. If both invposition of the breaker contacts.

9 dicators were energized the attendant would know immediately the breaker was tripped open and must be reset and then reclosed.

As previously stated, two or more circuit breakers may be assembled and tied together for unitary operation to control a multi-phase circuit. While only a single circuit breaker has been described, the breakers to be assembled are identical, hence, oniy the meansfor providing unitary operation of two or more circuit breakers will be described. When two or more breakers are assembled togetherythe plates m9 together with the mounting feet are omitted except those on the outside of the end breakersand the'break- -ersare secured together Iby means of a plurality of bolts 225 (Figs. 1 and 2) passing through all oi i the .assembled breakers-and h'avingnuts 221 fthreadedlyengaging the endsthereof.1 The trip -shafts |65 and the vlatch-members 65 are-tied'together for unitary movement by means of a sleeve 229 (Fig. 2) which couples the shafts |65 so that a tripping operation of the latch member 65 for one of the breakers in response to an overload current occurring in the related phase circuit will operate the latch members for all of the breakers. The operating shaft |95 described for the single pele breaker is replaced by a similar shaft E3| (Fig. 2) which extends through all of the breakers and has secured thereto for movement therewith the operating arms |551 for each breaker. Operation of the shaft 23| will effect manual opening and closing of the contacts of all of the breakers, reset and relatch the mechanism and reclose the contacts of all the breakers in the same manner as was described for the single pole unit.

The supply conductor 2631 for the indicator device of each phase breaker is provided at one end with a spring clip 233 (Fig. 2) for releasably receiving the externally projecting end of the conductor of the adjacent phase breaker so that the supply circuit extends through all of the breakers. The supply conductors 2|9 are grounded to their respective metallic housings.

From the foregoing description, it will be apparent that there is provided a circuit breaker embodying a tripping mechanism controlled by a thermally responsive element for opening the breaker contacts under certain overload current or temperature conditions and for effecting an indication of the condition of the breaker operating mechanism. There is also provided a second trip mechanism controlled by the thermally responsive element for eiecting an indication of the approach of a dangerous overload or temperature condition of a lesser magnitude than that required to trip the breaker, The arrangement of the trip mechanisms being such that in the event the condition which caused operation of the second trip mechanism disappears without having tripped the breaker, the trip mechanism may be reset by partial operation of the breaker operating mechanism without disturbing the There is also provided independent adjusting means for adjusting the trip mechanism to vary the amount of overload current required to trip the breaker and for independently adjusting indicating trip v mechanism to vary the amount of overload and/or temperature rise required to eect an indication without tripping the breaker.

Having described the invention in accordance with the patent statutes, it is to beV understood that various changes and modifications may be made in the structural details thereof without 'l0 departing from someof the essential features o the invention.

We claim as our invention:

1. In a circuit breaker comprising relatively movable contacts, operating mechanism yfor said contacts comprising a manually operable member, an actuating member, an overcenter spring operable by said manually operable member to operate said actuating member, cam means for controlling the tension of said overcenter spring during an operation thereof, a toggle normally engaging the actuating member and operable thereby to open and close said contacts, and a trip device operable to effect operation of said toggle to open said contacts irrespective of the position of the manually operable member and said actuating member.

2. In a circuit breaker comprising relatively movable contact means, operating mechanism for said contact means comprising a manually operable member, an actuating member, an overcenter spring operable by said manually operable member to operate said actuating member, fixed cam means disposed to effect radial movement of one end of said overcenter spring relative to said manual operable member during an operation thereof, a toggle separably engaging said actuating member and operable thereby to open and close said contact means, and trip means operable in response to overload currents to effect operation of said toggle independently of said actuating member to cause automatic opening of said contact means.

3. In a circuit breaker comprising relatively movable contacts, operating mechanism for said contacts comprising an actuating member, an overcenter spring having one end connected to said actuating member, a manually operable member related to the other end of said overcenter spring for operating said spring to eiect operation of said actuating member, cam means supporting said other end of said overcenter spring for causing movement of said other end of said overcenter spring relative to said manually operable member during an operation to keep the tension of said overcenter spring substantially constant until it moves overcenter, a toggle normally engaging said actuating member and operable thereby to open and close said contacts, and a trip device operable to effect disengagement of said toggle from said operating mechanism and spring of said contacts irrespective of the position of said actuating member.

4. In a circuit breaker comprising relatively movable contact means, operating mechanism for said contact means comprising an actuating member, a manually operable member, an overcenter spring having one end associated with said manually operable member and the other end connected to said actuating member, said overcenter spring being operable by said manually operable member to operate said actuating member, cam means disposed to effect movement of said one end of said overcenter spring relative to said manually operable member during an operation thereof to keep said one end of said overcenter spring at substantially the same distance from the other end thereof connected to said actuating member until it moves overcenter near the end of a closing operation, a toggle normally engaging said actuating member and operable thereby to open and close said contact means, said toggle at times being disengaged from said actuating member to eiect automatic open- 1 1 ing of said contact means irrespective of the position oi. said actuating member.

5. In a circuit breaker comprising relatively movable contact means, operating mechanisms for said contact means comprising an operating shaft, manual means for operating said shaft. a pair of spaced arms on said shaft, said arms be ing provided with radially extending parallel slots, an actuating member, an overcenter spring said toggle independently of said actuating member to effect automatic opening of said contacts.

JOHN K. HODNETTE. MERRILL G. LEONARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,169,586 Leonard Aug. 15, 1939 2,210,262 Sachs Aug. 6, 1940 2,240,189 Linde et a1. Apr. 29, 1941 2,284,825 Jennings et al June 2, 1942 2,306,090 Tate Dec. 22, 1942 2,306,235 Walle Dec. 22, 1942 2,318,279 Aschwanden May 4, 1943 2,501,363 Toth Mar. 21, 1950

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