US2165511A

US2165511A - Circuit breaker

Info

Publication number: US2165511A
Application number: US111801A
Authority: US
Inventors: Sandin Jerome
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1936-11-20
Filing date: 1936-11-20
Publication date: 1939-07-11
Anticipated expiration: 1956-07-11

Description

J. SANDIN CIRCUIT BREAKER July 11, 1939.

Filed.Nov. 20, 1936 2 Sheets-Sheet l WITNESSES:

17% fim m/ J. SANDIN CIRCUIT BREAKER July 11, 1939.

Filed Nov. 20, 1936 2 Sheets-Sheet 2 INVENTOR Jerome Sandi.

ATTORNEY WITNESSES:

Patented July 11, 1939 UNITED STATES PATENT OFFKIE CIRCUIT BREAKER Pennsylvania Application November 20, 1936, Serial No. 111,801

17 Claims.

My invention relates, in general, to circuit controlling devices and more particularly to field discharge circuit breakers.

Field discharge circuit breakers are used to protect the shunt field winding of large separately excited generators. When the shunt field winding of a separately excited generator is disconnected from its normal voltage supply by a circuit breaker, an excessive voltage may be induced in the winding which in many instances is sufficient to break down the insulation of the winding. For protection against such conditions, it is desirable to equip the circuit breaker in such application with a field discharge switch attachment which closes when the breaker opens to connect a resistor across the shunt field Winding for discharging the induced voltage, and which opens an instant before the breaker closes. A circuit breaker so equipped is referred to as a field discharge circuit breaker.

The problem of designing. a satisfactory field discharge circuit breaker has been exceedingly difiicult of solution. One type consists of a knife type field discharge switch coupled to the circuit breaker operating mechanism by an adjustable link and ratchet and pawl device. This form of coupling permits a certain amount of lost motion between the two, so that by properly adjusting the link, the discharge switch could be made to close an instant before the main contacts of the breaker separated and to open an instant before the main contacts closed. This arrangement has not proved entirely satisfactory, and could not successfully be applied to the later type of circuit breakers which embody quick make and break operation. Frequent adjustment of the link was necessary to ensure proper timing of operation of the discharge switch, and the sequence of operation was often destoyed by incomplete and rapid operations of the circuit breaker. The speed of operation of the circuit breaker soon resulted in failure of operation of the discharge switch.

The butt type of contact was found to be more desirable than the knife type, but when used in a field discharge switch, the high speed operation produced bouncing of the contacts resulting in the production of a series of secondary interruptions and high inductive voltages.

The principal object of my invention is the provision of an improved field discharge circuit breaker which is simple, more reliable and efficient in operation, and which can be morereadily and economically manufactured and installed than field discharge breakers heretofore known in the art.

Another object of my invention is. the provision of an improved field discharge circuit breaker embodying a field discharge switch attachment which makes and breaks contact at the proper instants during operation of the breaker without preliminary or subsequent periodic adjustments of any kind.

Another object of my invention is the provision of an improved field discharge circuit breaker embodying butt type field discharge contacts which are so mounted that they will not produce any objectionable series of secondary interruptions due to bouncing of the movable contact.

Another object of my invention is the provision of a field discharge switch attachment which will operate efliciently when applied to a circuit breaker embodying quick make and break action.

Another object of my invention is the provision of a field discharge switch attachment for a cir cuit breaker which will not lose its sequence of "operation with respect to the main contacts of the breaker under any operating conditions.

The novel features that I consider characteristic of my 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 of a specific embodiment thereof when read in connection with the accompanying drawings, in which:

Figure l is a plan view of my improved field discharge circuit breaker, with a portion of the cover broken away and the operating mechanism of the breaker omitted to illustrate the details of the field discharge switch attachment.

Fig. 2 is a vertical sectional view of the field discharge circuit breaker illustrated in Fig. 1, taken on the line II--II thereof, showing the details of the field discharge switch and the operating mechanism of the breaker.

Fig. 3 is a fragmentary sectional View showing the main contact means of the breaker in closed circuit position; and,

Fig. 4 is a schematic wiring diagram illustrating the manner in which the elements are connected in circuit.

Referring to the drawings, the field discharge circuit breaker illustrated in Figs. 1 and 2 comprises, in general, a base 1, a cover 9, contact means indicated generally at H, terminal means 13, an operating mechanism indicated generally at I5 for controlling the contact means, are extinguishing means I! extinguishing the arcs formed incident to opening of the contact means,

a removable unitary trip device indicated generally at l9 and a field discharge switch attachment indicated generally at 2!.

The structural details, functions and operations of the above referred to elements with the exception of the field discharge switch attachment are identical to the corresponding elements of the circuit breaker disclosed in the patent No. 2,047,739 issued on July 14, 1936, to H. J. Lingal and assigned to the assignee of this invention, except that in the present structure the contact means and associated arc extinguishing means of the center pole of the breaker have been omitted and in their place has been substituted the improved field discharge switch attachment of my invention indicated generally at 2 l. Only a brief description of the structure, function and operation of the main elements of the circuit breaker will be given in this application, since, for details, reference may be had to the above referred to patent.

The base 1 of the circuit breaker is of molded insulating material and has mounted thereon the terminal means l3, the unitary trip device is, the operating mechanism [5, the contact means I I, the arc extinguishing means ll, and the field discharge switch 2l. The base 7 and cover 9, which is also of molded insulating material, form a casing for enclosing the elements and mechanisms, which is divided into three longitudinal compartments 23 by partitions 25 (only one being shown). The outer compartments 23 house the contact means and associated arc extinguishing means of the outer poles of the circuit breaker while the central compartment houses the operating mechanism l5 and the field discharge switch attachment 2|.

The contact means and associated are extinguishing means of the two poles of the circuit breaker are identical and hence a description of the contact means and associated arc extinguishing means of one pole of the breaker will be sufficient. Referring to Fig. 3, the contact means comprises, in general, a stationary main contact 21, a stationary arcing contact 29, a movable contact member 3i carrying the movable main contact 33 and the movable arcing contact 35, a channel shaped movable switch arm 31 for pivotally supporting the contact member 31 and a spring means 39 for biasing the contact carrying portion of the movable contact member 3| toward the

stationary contacts

27 and 29.

The channel shaped switch arms 37 of the two poles of the breaker are rigidly secured for movement together by means of a movable switch member or tie bar M of insulating material. Each of the channel shaped switch arms is secured to the tie bar by means of the U-shaped strap 43. The switch member ll and the switch arms 31 are mounted for movement between an open circuit position and a closed circuit position. When the switch member 4i moves to closed circuit position, the movable arcing contacts of each pole of the circuit breaker first engage their cooperating stationary arcing contacts 29 and slight further movement towards closed circuit position causes the movable contact members 3| to be pivoted about their pivot pins so as to engage the

main contacts

33 and 27 and subsequently separate the arcing

contacts

35 and 29. In moving to the open circuit position, substantially the reverse action takes place. In the first part of the opening movement, the springs 39 cause the movable contact members to pivot about the pins 35 so as to engage the arcing

contacts

35 and 29 an instant before separation of the

main contacts

33 and 21. By this means the are formed incident to the separation of the contacts is always struck between the

arcing contacts

35 and 29,

The are extinguishing means indicated generally at I! is not an important part of my invention, and any suitable type of arc extinguishing means may be used. One particularly effective form is described in the patent of M. W. Brainard, No. 1,896,764 which was issued February 7, 1933, and which is assigned to the assignee of this invention.

The operating mechanism of the circuit breaker is located in the central compartment 23 and coniprises, in general, a main U-shaped frame M, an operating member 49, a pair of toggle links 5! and 53, a releasable actuating member 55, overcenter springs 57, and a channel shaped switch arm 59. the operating member 49 are pivotally supported by means of a pair of pins to the U-shaped supporting frame 47. The toggle links 5i and 53 pivotally connect the channel shaped switch arm 59 to the releasable actuating member 55. The over-center springs 51 are connected in tension between the top of the operating member 49 and the knee pivot pin which connects the toggle links 5| with the links 53. The channel shaped switch arm 59 is pivotally supported by a pivot pin 6! to the side walls of the U-shaped main frame 41 and is connected for simultaneous movement with the channel shaped switch arms 37 of the outer poles of the circuit breaker by means of a metal strip 43, which connects it to the switch 1 member or tie bar 4|.

The releasable actuating member 55 is adapted to be held in latched-in position by means of a slidably pivoted latch member 63, which is biased to latching position by means of spring 55. The latch 63 is slidably and pivotally supported by means of a U-shaped bracket 67 and forms part of the trip device indicated generally at 19. The

details of construction and the operation of the trip device which I prefer to use with this invention are completely described in the previously referred to Patent No. 2,047,739. The free end 69 of the latch member 63 projects through an opening in the base H of the trip device and is adapted to be engaged and held in latched position by means of a latch plate carried by a trip bar mounted within the casing 13 of the trip device. The trip bar (not shown) extends transversely across the two poles of the circuit breaker and is adapted to be actuated to tripping position to release the latch 63 by a plurality of electromagnetic and/or bimetallic trip elements, there being one electromagnetic element and one bimetallic trip element contained in the casing 73 for each of the two poles of the circuit breaker, the trip elements for each pole being connected in circuit with their corresponding contact means. The casing 13 of the trip device is mounted transversely in a compartment provided in the casing formed by the base I and the cover 9 of the circuit breaker, and the trip device is adapted to be removably mounted in the casing and connected in circuit with the poles of the circuit breaker by means of screws 75 and terminals l3.

The circuit for the two poles of the circuit breaker are identical, and a description of the circuit for only one pole will be given. The circuit extends from the upper end terminal l3 to the The releasable trigger member 55 and stationary main and arcing

contacts

21 and 29 7 through the movable main and arcing

contacts

33 and 35, movable contact member 3 I, flexible shunt conductor TI, to the terminals of the trip device through the electromagnetic and bimetallic trip elements, to the lower end terminal I3 of the circuit breaker.

The operation of the circuit breaker as thus far described is as follows: With the operating member 49 in the closed circuit position shown in Fig. 2, and the contact means in the closed circuit position, let it be assumed that it is desired to open the contact means of the circuit breaker. The operating member 49 is moved by means of the handle 83 in a clockwise direction to the opposite end of the slot provided in the cover 9. The movement of the operating member 49 to the open circuit position for opening the contact means ll causes the overcenter springs 5'! to change their line of action, which causes collapse of the toggle links 5! and 53. The collapse of the toggle links 5| and 53 causes the central switch arm 59 to be partially rotated with a snap action about its pivot pin 6! to the open circuit position. The channel shaped switch arms 31 of the two poles of the circuit breaker are moved to open circuit position simultaneously with the movement of the central channel shaped switch arm 59 by reason of the fact that they are connected to the central switch arm 59 by means of the tie bar 4|. The movement of the switch arms 37 to the open circuit position first causes engagement of the arcing

contacts

35 and 29 and an instant later the separation of the

main contacts

33 and 21. Further opening movement of the switch arms 37 causes separation of the arcing

contacts

35 and 29, and interruption of the circuits controlled by the poles of the breaker. The are formed incident to the separation of the

contacts

35 and 29 is extinguished by means of the arc extinguishing means II. If it is desired to reclose the circuit breaker the operating member 49 is moved in a counter-clockwise direction to the position shown in Fig. 2 and substantially the reverse action takes place. At a predetermined point in the movement of the operating member 49 to closed circuit position the overcenter springs 57 change their line of action and cause the toggle links SI and 53 to assume extended or toggle position to effect movement of the switch arm 59 and switch arm 31 to their closed circuit position with a snap action. During the latter part of the movement of the switch arms 3'! to closed circuit position, the arcing

contacts

35 and 29 are first engaged, and after slight further movement partial rotation of the movable contact members 3| effects engagement of the

main contacts

33 and 21. Slight further movement of the switch members 31 to final closed circuit position effects separation of the arcing

contacts

35 and 29.

In the preceding description of the manual operation of the circuit breaker, the trigger member 55 was assumed to be held in its normal latched-in position by means of the trip device 59 and its latch member 63. With the circuit breaker in the closed circuit position, when an overload of predetermined magnitude occurs in the circuit of either pole of the circuit breaker, the corresponding electro-magnetic or thermal bimetallic trip element of the trip device causes movement of the trip bar to releasing position to eifect release of the latch member 63. When the latch member 63 is released, the trigger member 55 is moved by a component of the force exerted by the overcenter springs 51 in a counterclockwise direction. The movement of the trigger member 55 in a counter-clockwise direction causes the overcenter springs 51 to change their line of action and cause collapse of the toggle links 5| and 53. The collapse of the toggle links 5! and 53 effects the opening of the contact means of each pole of the breaker in a manner previously described.

After the tripping operation, as above described, has occurred, the circuit breaker cannot be manually reclosed until the trigger member 55 has been reset in its latched-in position. For the purpose of resetting trigger member 55, the operating member 49 is provided with a hook shaped reset member 19 which is adapted to engage and move the trigger member 55 to latched-in position. To reset the breaker after a tripping operation, the operating member 49 is moved to the full open-circuit position. During movement of the operating member 49 to the open-circuit position, the reset member l9 engages and moves the trigger member 55 in a clockwise direction to its latched-in position in which it is reengaged and held by the latch member 63. The breaker may now be reclosed manually by movement of the operating member 49 to the closed circuit position in a manner previously described.

The operating member 49 has secured to the top thereof an arcuate closure member BI and an operating handle 83. The closure member 8| is adapted to cover the slot provided in the cover for the operating handle 83 in any position of the operating member 49 and handle 83.

The field discharge switch attachment which forms a part of the circuit breaker is mounted in the central longitudinal compartment 23 and comprises, in general, a stationary contact indicated generally at 85, a movable contact indicated generally at 81, a pivoted actuating or switch arm 89, a U-shaped switch arm support 9|, and end terminals 93 for connecting the contact means of the field discharge switch in an external circuit.

The stationary contact comprises a contact tip 95 secured to a resilient contact supporting arm 9?. The stationary contact supporting arm 91 is secured to the terminal 93 by means of rivets 99. The terminal 93 comprises a metal strip I9! of the shape shown in Fig. 2 which has one end clamped to the base by means of the nut and bolt assembly I53 and the other end thereof secured to the base I of the breaker by means of a nut bolt and washer assembly 35. The movable contact, indicated generally at 87, comprises a U-shaped movable contact member H3? which has an extension I99 forming a movable contact tip for cooperation with the stationary contact tip 95. The legs of the U-shaped movable contact member are pivotally supported on one end of the actuating or switch arm 89 by means of the pivot pin H9. The legs of the movable contact member l0! have angularly extending flanges Hi formed integral therewith to each of which is secured a weight member H3. The pivoted contact member Ill! is biased in a counter-clockwise direction by means of a coil spring 5 l2 which has its body portion coiled about the pivot pin H5 and its free ends respectively engaging under tension the contact portion 199 and the actuating arm 89. The contact tip i 95 is provided with an angular stop projection lid which normally engages the switch arm 89 to limit counter-clockwise rctation of the contact tip 59 about its pivot pin I Ill. The contact tip I09 is thus biased to normally occupy a certain angular position with respect to the switch arm 89. The actuating arm 89 is channel-shaped in cross-section and is pivotally connected to the U-shaped supporting member by means of a pivot pin H5. The end of the switch arm 89 opposite that carrying the movable contact IT has pin receiving recesses I I1 formed at the end of each of the legs of the switch member. The recesses II'I are adapted to receive a pin I I 9 supported transversely between the side walls of the central switch arm 59. The recesses Ill and the pin II9 form a coupling means for connecting the switch or actuating arm 89 of the field discharge switch to the switch arm 59 of the circuit breaker.

The U-shaped supporting frame 9| is secured to the base I of the circuit breaker by means of a screw I2I and a lock washer I23. The lock washer I23 is adapted to engage against a metal insert I25 seated in a recess I2I formed in the under side of the base 'I of the circuit breaker. The movable contact member IN is adapted to be connected in circuit with the lower terminal 93 by means of a flexible shunt conductor I29 which has one end secured to the movable contact tip I09 by screw I3I and the other end thereof secured to a conducting strip I33 by means of a screw I35. The conducting strip I33 forms an integral part of the end terminal means 93 and extends from the contact supporting frame 9I to which it is secured by means of the screw I2 I, beneath the operating mechanism l5 and the trip device I9 to the lower terminal recess of the circuit breaker. The terminal end of the strip I33 is secured to the base of its terminal recess by means of a nut and bolt assembly I03 similar to that shown at the upper end of the breaker.

The circuit for the field discharge switch extends from the upper terminal 93 through the resilient stationary contact supporting arm 91, the stationary contact 95, the movable contact member I01, the flexible shunt conductor G29 to the conductor strip I33 to the lower end terminal 93.

The operation of the field discharge switch in connection with the operation of the circuit breaker is as follows. With the parts of the circuit breaker in the position shown in Fig, 2, that is, with the operating handle 83 and the main contact means of the breaker in closedcircuit position, the contacts 95 and I9 of the field discharge switch are in the open-circuit position. When the main movable contacts. 3| of the circuit breaker are moved to the opencircuit position, either by a manual operation or by a tripping operation, as described in a preceding paragraph, switch arm 59 through the coupling means comprising the pin H9 and the recesses II'I, moves the actuating arm 89 in a counter-clockwise direction about its pivot pin II5 to cause the movable contact member ml to move downwardly so as to engage the contact tip I09 with the stationary contact tip 95. The arrangement is such that the contact tip I99 engages the stationary contact tip 95 an instant before separation of the arcing

contacts

35 and 29. As has been previously pointed out, the switch member 59 which actuates the movable switch arms of the circuit breaker moves to open and to closed circuit position with a snap action. This results in similar but oppositely directed movements of the actuating arm 89 about its pivot pin H5. The weight H3 is provided for the purpose of overbalancing the contact tip I09, so that its inertia prevents the contact tip I09 from lagging behind during movement of the switch arm 89. When the switch arm 59 starts to move toward open-circuit position to open the main contacts of the breaker, the inertia of the weight II3 causes them to tend to remain stationary so that the contact tip I09 maintains its normal angular position with respect to the switch arm 89 during the closing movement thereof until it engages the stationary contact tip 95. The contact tip I09 is thus prevented from lagging behind the switch arm 89 during its rapid movement toward closed circuit position. The contact tip I09 engages the stationary contact tip 95 an instant before separation of the contacts of the breaker and further opening movement of the switch arm 59, which causes separation of the breaker contacts, causes the movable contact member I0'I of the field discharge switch to pivot about the pin H0 in a clockwise direction, so as to tension the coil spring I 52. The coil spring IIZ thus provides a high contact pressure between the movable contact tip I99 and the stationary contact tip 95.

Due to the rapid snap acting movement of the actuating arm 09, effected by movement of the switch arm 59 to the open circuit position with a snap action, the movable contact member I0! is subject to a certain amount of bouncing when it engages the stationary contact tip 95. The resilient mounting of the stationary contact tip 95, however, causes the same to remain in engagement with the movable contact tip I09 dur ing the entire series of oscillations due to bouncing and thus effectively prevents any secondary interruption of the circuit controlled by the field discharge circuit.

When the main movable contact members 3I of the circuit breaker are moved to closed circuit position by the movement of the switch arm 59 to its closed circuit position, the actuating arm 89 of the field discharge switch is moved in a clockwise direction about its pivot pin H5. The inertia of the weights II 3 tends to keep them stationary so that the contact tip I09 initially moves away from the stationary contact tip 95 at a more rapid rate than that of the end of the switch arm 89. The inertia of the weights II3 also prevents any premature clockwise rotation of the contact tip I09 about its pivot pin H0 by the spring II2.

It will thus be seen that the structure of the field discharge switch is such that the contacts thereof are closed an instant before separation of the breaker contacts, and separate .at an instant before closure of the breaker contacts and that any secondary interruptions of the circuit controlled by the field discharge switch due to bouncing are prevented by the resilient mounting of the stationary contact of the field dis.- charge switch. The coupling means, whereby the actuating arm 89 of the field discharge switch is connected to the switch arm 59 or operating member of the circuit breaker, constitutes a decided improvement over the ratchet type of coupling means heretofore used with field discharge switches. The coupling means of the present invention precludes any possibility of the field discharge switch losing its sequence of operation with respect to the contacts of the breaker.

Fig. 4 illustrates schematically the connection of the field discharge circuit breaker with the shunt field winding of a separately excited generator and with the field discharge resistance.

LI .and L2 represent the normal voltage supply lines for the shunt .field winding I 36 of a separately excited generator. Included in series circuitwith the supply lines LI and L2 are the main contacts 2! and 33 and the arcing

contacts

29 and 35 of the field discharge circuit breaker, The field discharge resistance I31 has one terminal thereof connected to the supply line Li on the shunt field winding side of the circuit breaker. The other terminal of the field discharge resistance is connected to one of the end terminals 93 of the field discharge switch 2| of the circuit breaker. The other terminal 93 of the field discharge switch 2| is connected to the supply line L2 between the circuit breaker contacts and the shunt field winding of the generator.

When the contacts of the circuit breaker are opened to disconnect the shuntfield winding of the generator from its normal voltage supply, the field discharge switch 2| connects the field discharge resistance I 3'! across the terminals of the shunt field winding in order to discharge the voltage induced in the winding caused by separation of the breaker contacts. Likewise, when the circuit breaker is closed to connect the shunt field Winding to its normal voltage supply, the field discharge switch is automatically opened an instant before closure of the main contacts in order to disconnect the field discharge resistance 53! from the supply lines LI and L2.

While I have shown and described a field discharge switch attachment associated with a specific circuit breaker structure, it is obvious that my improved field discharge switch structure is equally applicable to other forms of circuit breaker structure. For example, the contact means of the circuit breaker described and illustrated are of the type comprising main and arcing contacts. It can be readily seen that the field discharge switch attachment disclosed is equally applicable to a circuit breaker structure in which different types of contacts are employed. In the appended claims the expression main contacts is intended to refer to the contacts of a circuit breaker which function to open or to close the main circuit or circuits controlled by the breaker.

It will thus be seen that I have provided an improved field discharge circuit breaker which is reliable and highly efficient in operation, which embodies the advantages of the butt type contacts without their disadvantages due to bouncing. My improved field discharge circuit breaker also embodies a novel form of coupling means between the field discharge switch and the operating mechanism Or main switch arms-of the breaker which precludes the possibility of the field discharge switch losing its sequence of operation with respect to the operation of the breaker contacts and which requires no preliminary or subsequent periodic adjustments in order to insure proper time of closure and separation of the field discharge contacts.

While, in accordance with the patent statutes, I have given the foregoing details of a practical embodiment of my invention, it is to be understood that many of these are merely illustrative, and that variations of their precise form may be had without departing from the spirit of the invention. I desire therefore that the language of the accompanying claims be accorded the broadest reasonable construction, and that my invention be limited only by what is explicitly stated in the claims and by the prior art.

I claim as my invention:

1. A field discharge switch attachment for a circuit breaker having relatively movable contacts, a switch member movable to an open and to a closed circuit position to open and close said contacts, and an operating means for moving said switch member to open or closed circuit position with a snap action, said field discharge switch attachment comprising a resiliently mounted stationary butt contact, a pivoted actuating member, a movable butt contact pivotally mounted adjacent one end of said actuating member, spring means for biasing said movable contact toward said stationary contact, weight means carried by said movable contact for overbalancing the same so as to prevent said movable butt contact from lagging behind said actuating member during'movement thereof, and means coupling said actuating member to said switch member for movement thereby in an opposite sense from that of said switch member so that said butt contacts open on closure of said breaker contacts and close on separation of said breaker contacts.

2. In a circuit breaker having relatively movable contact means and an operating member movable with a snap action to open or to close said contact means, a field discharge switch comprising a stationary contact, a pivoted switch arm, a movable contact pivotally mounted adjacent one end of said arm for cooperation with said stationary contact, spring means biasing said movable contact toward said stationary contact, weight means secured to said movable contact for overbalancing the same to prevent said movable contact from lagging behind said switch arm during movement thereof, and means for coupling said switch arm to said operating member so that said field discharge switch contacts engage an instant before separation of said breaker contacts and separate an instant before closure of said breaker contacts.

3. An electric switch comprising a resiliently mounted stationary. contact, a pivoted switch arm, a movable contact pivoted to said arm adjacent one end thereof, spring means biasing said movable contact toward said stationary contact, weight means secured to said movable con tact for overbalancing the same, an operating member coupled to the end of said switch arm opposite said contact carrying end for moving said switch arm to open or to closed circuit position with a snap action, the inertia of said weight means preventing said movable contact from lagging behind said switch arm during movement thereof.

4. In a circuit breaker, the combination of relatively movable contacts, a switch member movable to an open or to closed circuit position to open or to close said contacts, operating mechanism for moving said switch member to open or to closed circuit position with a snap action, a field discharge switch comprising a resiliently mounted stationary contact, a pivoted switch arm, a movable contact member pivotally mounted on said arm adjacent one end thereof, said contact member having a contact portion located on one side of the pivot point thereof and a weight means secured to said contact member on the opposite side of the pivot point thereof, spring means acting on said contact member for biasing the contact portion toward said stationary contact, means coupling the end of said switch arm opposite that carrying said contact member to said switch member for movement thereby so that the contacts of said field discharge switch close an instant before separation of said breaker contacts and separate an instant before closure of said breaker contacts, the inertia of said weight means preventing said movable contact portion from lagging behind said switch arm during movement thereof, said resilient mounting of the stationary contact preventing secondary interruptions by said field discharge switch due to bouncing of said contact member.

5. A field discharge circuit breaker comprising, in combination, a casing provided with three compartments, relatively movable contact means mounted in two of said compartments to form two main poles of the circuit breaker, a common operating mechanism for simultaneously opening or closing all of said contact means mounted in the other of said compartments including a common operating member extending into each compartment and connected to said contact means, a field discharge switch mounted in said other compartment, and means coupling said field discharge switch to said operating member so that said field discharge switch opens when said contact means close and closes when said contact means open.

6. A multiple field discharge circuit breaker comprising, in combination, a casing divided into a plurality of compartments, a stationary and a cooperating movable contact mounted in each compartment except one to form a plurality of poles, a common operating mechanism mounted in said one compartment for simultaneously moving all of said movable contacts to open or to closed circuit position, said operating mechanism including a common operating member extending into each of said compartments and connected to said movable contacts, a common trip device including a plurality of individual electroresponsive trip means one for each pole of the breaker operable in response to predetermined conditions to cause said operating mechanism to move said movable contacts to open circuit position, means for removably mounting said trip device in said casing, a field discharge switch mounted in said one compartment, means coupling said field discharge switch directly and continuously to said common operating member so that it opens when said contacts close and closes when said contacts open.

7. In a multi-pole circuit breaker, a base member, three pairs of separable contact members mounted on said base member in side-by-side relation, an operating mechanism for a threepcle circuit breaker connected to each of said three pairs of contact members, said operating mechanism having a single handle member movable between two positions, and said operating mechanism moving two of said pairs of contacts to open position and the third pair of contacts to closed position upon movement of said handle to one position and moving said two pairs of contacts to closed position and said third pair of contacts to open position upon movement of said handle to its other position, and current responsive means for causing said operating mechanism to move said two pairs of contacts to open position and the third pair of contacts to closed position upon the occurrence of a predetermined condition.

8. In a multi-pole circuit breaker, a base having spaces for mounting three pole units thereon in side-by-side relation, a single operating mechanism for a three-pole circuit breaker mounted on said base in line of said spaces, two pairs of contacts for connection in the main circuit positioned in the other two of said spaces and a third pair of contacts mounted in the space with the operating mechanism for connection in an auxiliary circuit, a contact actuating bar movable by said operating mechanism extending across said base and connected to move said two pairs of contacts to closed position and said third pair of contacts to open position when moved in one direction, and current responsive means operable in response to predetermined conditions for causing said operating mechanism to move said bar in the opposite direction and move said two pairs of contacts to open position and said third pair of contacts to closed position.

9. In a circuit breaker, relatively movable breaker contacts, a switch member movable to open and to closed circuit position for opening and closing said breaker contacts, an auxiliary switch comprising a contact carrying arm connected directly and continuously to said switch member for movement thereby to a closed circuit position by movement of said switch member to open circuit position and to an open circuit position by movement of said switch member to closed circuit position, a movable contact mounted on said arm for movement thereby and for limited movement relative thereto, a cooperating stationary contact engageable by said movable contact, and means acting on said movable contact for causing said auxiliary switch contacts to close an instant before opening of said breaker contacts and to open before closing of said breaker contacts.

10. In a circuit breaker, relatively movable breaker contacts, a switch member movable to open and to closed circuit position for opening and closing said breaker contacts, actuating means for moving said switch member to open and to closed circuit position with a snap action, an auxiliary switch comprising relatively movable contacts, a contact carrying arm connected directly and continuously to said switch member for direct movement thereby to an open circuit position by movement of said switch member to closed circuit position and to a closed circuit position by movement of said switch member to open circuit position for actuating said auxiliary switch contacts, one of said auxiliary switch contacts being mounted on said arm for movement thereby and for limited movement relative thereto, and means acting on said contact carried by said arm for 5 11. In a circuit breaker, relatively movable 2' breaker contacts, a switch member movable with a snap action to open and to closed circuit position for opening and closing said breaker contacts, an auxiliary switch comprising a contact carrying arm connected directly and continuously to said switch member for direct movement thereby to an open circuit position by movement of said switch member to closed circuit position and to a closed circuit position by movement of said switch member to open circuit position, a movable contact pivotally mounted on said arm for movement thereby and for limited pivotal movement relative to said arm, a cooperating stationary contact engageable by said movable contact, and means acting on said movable contact for causing said auxiliary switch contacts to engage an instant before separation of said breaker contacts, and to separate before said breaker contacts engage.

12. In a field discharge circuit breaker, a plurality of pairs of relatively movable butt type breaker contacts, a switch member movable to open and to closed circuit position for simultaneously opening and closing all of said pairs of breakers contacts, operating means for moving said switch member to open and to closed circuit position with a snap action, an auxiliary switch comprising a contact carrying arm connected di-- rectly and continuously to said switch member for movement thereby to an open circuit position by movement of said switch member to closed circuit position and to a closed circuit position by movement of said switch member to open circuit position, a movable contact mounted on said arm for movement thereby and for limited movement relative thereto, a cooperating stationary contact engageable by said movable contact, and means acting on said movable contact for causing said auxiliary switch contacts to engage an instant before separation of said breaker contacts, and to separate before said breaker contacts engage.

13. In a circuit breaker, relatively movable butt type breaker contacts, a switch member movable to open and to closed circuit position for opening and closing said breaker contacts, operating means for moving said switch member to open and to closed circuit position with a snap action, a field discharge switch comprising a relatively stationary butt type contact, a cooperating movable butt type contact, an arm carrying said movable contact, said arm being connected directly and continuously tosaid switch member for movement thereby to close said field discharge switch during opening movement of said switch member and to open said field discharge switch during closing movement of said switch member and means for causing said field discharge switch contacts to engage an instant before separation of breaker contacts, and to open before said breaker contacts engage.

14. In a circuit breaker, relatively movable butt type breaker contacts, a switch member movable to open and to closed circuit position for opening and closing said breaker contacts, operating means for moving said switch member to open and to closed circuit position with a snap action, a field discharge switch comprising a resiliently mounted stationary butt type contact, a cooperating movable butt type contact, an arm carrying said movable contacts, said arm being connected directly and continuously to said switch member for movement thereby to close said field discharge switch during opening movement of said switch member and to open said field discharge switch during closing movement of said switch member and means for causing said field discharge switch contacts to engage an instant before separation of breaker contacts, and to open before said breaker contacts engage.

15. In a field discharge circuit breaker, relatively movable butt type breaker contacts, a switch member movable toopen and to closed circuit position for opening and closing said contacts, actuating means for moving said switch member to open and to closed circuit position with a snap action, a field discharge switch comprising a resiliently mounted butt type contact, a cooperating butt type movable contact pivotally mounted on a contact carrying arm, said arm being directly and continuously connected to said switch member for movement thereby toa closed position by movement of said switch member to open circuit position and to an open position by movement of said switch member to closed circuit position, means including a spring biasing said movable contact toward said stationary contact for causing said field discharge switch contacts to engage an instant before separation of said breaker contacts and means for causing said field discharge switch contacts to open before said breaker contacts engage.

16. In a circuit breaker, relatively movable breaker contacts, a switch member movable to open and to closed circuit position for opening and closing said contacts, actuating means for moving said switch member to open and to closed circuit position with a snap action, an auxiliary switch comprising relatively movable contacts, a contact carrying arm for actuating said auxiliary switch contacts connected directly and continuously to said switch member for movement thereby toa closed position by movement of said switch member to open circuit position and to an open circuit position by movement of said switch member to closed circuit position, one of said auxiliary switch contacts being mounted on said arm for movement thereby and for movement relative thereto, and means acting on said contact carried by said arm for causing said auxiliary switch contacts to engage an instant before separation. of said breaker contacts and to separate before said breaker contacts engage, said contact carrying arm being pivotally mounted intermediate its ends and directly connected to said switch member by a pin and slot connection.

17. In a field discharge circuit breaker, relatively movable breaker contacts, a switch member, movable to open and to closed circuit position for opening and closing said breaker contact, a snap acting mechanism for moving said switch member to open and to closed circuit position with a snap action, a field discharge switch comprising a stationary contact, a contact carrying arm connected directly and continuously to said switch member for movement thereby to a closed circuit position by movement of said switch member to open circuit position and to an open circuit position by movement of said switch member to closed circuit position, a movable contact member pivotally mounted on said arm for movement thereby and for limited pivotal movement relative to said arm toward and away from said stationary contact, spring means biasing said contact member about its pivot axis toward said stationary contact, and a weight means connected to said contact member on the opposite side of its pivot aXis from the contact engaging portion thereof, said spring means and said weight means acting to cause said field discharge switch contacts to engage an instant before separation of said breaker contacts and to separate before said breaker contacts engage.

JEROME SAN DIN