US2304253A - Circuit breaker - Google Patents

Description

Dec. 8, 1942. G, A; HEAUS 2,304,253

CIRCUIT BREAKER Filed March 6, 1940 3 Sheets-Sheet l /C g4, a ijf/Wu,

M ATTORNEY Dec. s, 1942. G. A. Hams 2,304,253

C IRCUIT BREAKER l NVENTO 650/2616 Aff/u /s ATTORNEY Dec. 8, 1942. G. A. HEADS CIRCUIT BREAKER Filed March 6,- 1940 3 Sheets-Sheet 3 l kBY Patented Dec. 8, 1942 2,304,253 CIRCUIT BREAKER George A. Healis, Aidan, Pa., assignor, by mesne assignments, to The Pennsylvania Company for Insurances on Lives and Granting Annuities, Philadelphia, Pa., a corporation of Pennsylvania Application March 6, 1940, Serial No. 322,444

(Cl. 20D-106) 6 Claims.

This invention relates particularly to air circuit breakers for use in industrial applications and for use on switchboards for the control of circuits.

The main object is to provide a breaker of this type of compact form, occupying comparatively small space and having a relatively high ampere interrupting capacity. It is adapted for use on circuits having voltages up to 600 or more and for normal currents of several hundred amperes, the interrupting capacity on overloads being far higher. Another object is to provide a separate enclosing apartment of improved form for each pole cf the breaker which may be assembled and disassembled readily and conveniently. Another object is to relate the contact parts in such a manner as to insure a firm and adequate engagement and to provide auxiliary contacts and associated means which will effectively withstand and reduce the arcing. Another object to is provide a related overload controlling means of improved form which will serve to impose a time delay of proper amount in its control under moderate overloads while serving to secure instantaneous opening of the breaker upon the occur- Other oband at right-angles to the shaft of the contact l arms showing the breaker closed; Fig. 3 is a vertical section through the mechanism compartment at right-angles to the shaft of the contact arms showing the parts when the breaker is closed; Fig. 4 is a similar view showing the parts when the breaker has been tripped; Fig. 5 is a similar view showing the parts in position for reclosing the breaker; Fig. 6 is a Vertical longitudinal section of one of the overload devices; and Fig. 7 is a view similar to Fig. 6 showing a modified form.

The breaker is shown mounted upon a rear insulating panel l and is enclosed by a metal casing 2 which surrounds the two sides, front and bottom of the breaker and has inwardly turned edges 2a at the top of the sides and an inwardly turned edge 2b at the top of the front, which edges embrace the top portion of the breaker. At each lower side of the breaker and within the casing is mounted a sheet metal support 3, the I rear portions ci these two supports being bent inwardly and secured to the back ofthe panel by bolts 3a. These supports form the bearings for the main shaft 4 of the breaker. This shaft is of square cross-section, as shown in Figs. 2 to 5, the ends of the shaft being round and being journaled in the supports 3. The square portion of the shaft is enveloped by insulating material 5 oi suitable thickness and carries insulating shields or disks 5a which extend outwardly beyond the insulation on the shaft. In the particular form shown, the breaker is a three-pole breaker having three sets of contacts adapted for use in a three-phase circuit. A contact arm 6 is provided for each phase and is xed to the main shaft at its lower end by being clamped thereto, as shown in Fig. 2. These movable contact arms shown are generally of T-angle form for strength having their faces toward the rear for engagement with fixed contacts and are composed of a material of high conductivity, such as forged copper. Intead of these arms being connected in circuit by the usual flexible conductor, they cooperate with contacts which are connected to the incoming and outgoing leads which avoids the necessity of connecting flexible leads to the contact arms.

Fig. 2 shows the form of the iixed contacts with which the arms 6 respectively cooperate, the parts being shown in closed circuit relationship. The xed contacts are each of similar form and include a lower Contact which remains in engagement with the arm 6 at all times, an upper main contact and an arcing contact above the main contacts. Considering iirst the lower main contact, this is in the form of a recessed or cupshaped copper block 'l having side plates 'Ia and forms a bearing with an open top portion. Pivotally mounted in this bearing is a pair of contact fingers B of copper, the end surfaces of these lingers having a bearing against the walls of the recess for securing a good conductive engagement. A pin lla mounted in the side plates 'la serves to retain the fingers in the recess, there being suilicient freedom of movement on the pin to permit the edge surfaces of the fingers to always maintain contact with the walls of the recess. 'I'he contact block is mounted on the panel I by a screw bolt 'lby which extends through from the back of the panel into the block. A stii spring S is introduced between the rear of the lingers 8 and an upwardly extending portion of the block l, an insulating disk 9h being located at the rear of the spring for preventing current from passing through the spring. The spring forces the front portions of the fingers 8 firmly against the lower face of the contact arm 6. A T-shaped piece of metal 9a is seated in notches on the inner edges of the contact fingers, the tongue portion of the T extending within the spring and serving to hold the front end of the spring in proper position in relation to the fingers. These lower main contact fingers are maintained in good electrical connection at their front upper ends with the lower portion of the contact arm in all positions thereof by the pressure of the spring, the lower ends of the fingers being forced against the walls of the block 'I in all positions. The pivotal support of the lower ends of the ngers in the block permits the fingers to move against the pressure of the spring when the contact arm is moved to closed position. The outside lead is connected to the bolt I which extends through the panel and is connected to a block at the inner end of the copper conducting strip Ila. This strip continues and is wound to form an overload coil II which is shown with its turns spaced apart from each other and having its rear end connected to the underside of the block 'I by a screw bolt 1c.

The upper main terminal is of the same form as the lower main terminal and is turned downwardly instead of upwardly, the parts being correspondingly numbered. The outside lead is connected to the bolt IDa which in turn is screwed into the rear of the block 'I to form a good electrical connection. The bolts I0 and IOa and the parts connected thereto are held in place by nuts IUI) which are threaded on the bolts and drawn up against a spacing bushing Ic.

The upper arcing contact is located above the upper main contact and is similar thereto, the corresponding parts being given the same reference characters. The faces of the fingers 8 of the arcing contact have secured thereto a metal face plate 8b of non-oxidizing and non-welding material which will not volatilize under the effects of any electric arc. The upper inner face of each contact arm 6 is similarly faced with a sheet 6b of similar material, the face plates 6b and 8b forming an auxiliary contact engagement when the breaker is closed, as shown in Fig. 2. The copper cupped-shaped block 'I of the arcing contact is extended forwardly somewhat and faced with a. plate 'Id of' non-oxidizing, nonwelding and non-volatilizing material. The upper block I is held in place on the panel I by a screw bolt Ib which passes through the panel and engages the rear of the block. The contact block 'I of each of the contacts is provided with a forward extension 'Ie which limits the outward movement of the fingers of the contacts when not engaged by the contact arm.

The fingers of the lower main contacts are directed upwardly while those of the upper con tacts are directed downwardly. It results that the magnetic field set up by the passage of current through the contacts and the contact arm, tends to force the fingers outwardly against the contact arms and thereby increases the contact pressure against the arms. This added pressure serves to improve the electrical Contact of the parts.

At the side of the auxiliary arcing contacts of each pole of the breaker is a magnetic blow-out coil I2 formed of a single turn of a metal copper strip positioned in a vertical plane, as shown in dotted lines in Fig. 2 and in ful1 lines in the upper right-hand sectionalized portion of Fig. 1.

CIX

Each of these three strips I2 has an end I2a 75 extending to one side and connected to the top of the upper block 'I while the other end of each coiled strip I2 has an extension I2b to one side which is connected to the top of the block 1 of the upper main contact.

The open position of each contact arm 6 is shown in dotted lines in Fig. 2. When the contact arm shaft 4 is turned to move the arm to its closed position, its face plate 6b first engages the face plate 8b of the arcing contact fingers and turns them downwardly away from the face plate Id and rearwardly towards the panel I against the pressure of the spring 9. Continued movement of the arm 6 brings it into additional engagement with the contact fingers 8 of the upper main contact and forces them inwardly against the pressure of their spring 9. Fig. 2 shows the parts in fully closed position, the cir cuit then passing from the lower bolt ID through the overload coil II to the lower main terminal block 'I to its fingers 8 and then through the arm 6 to the contact fingers 8 of the upper main terminal and then through the terminal block to the upper bolt Illa. When the contact arm 6 is moved to its open position, the contact between this arm and the fingers 8 of the upper main contact is interrupted first which results in the current passing from the upper end of the arm 6 through the contact plates 5b and 8b and through the fingers 8 to the block I of the arcing contact, then by the connection I 2a through the coil I2 to the upper main contact block I by the connection |21) and thence to the outside circuit through the bolt Illa. This creates a strong magnetic field across the arcing contacts. As the arm 6 continues to move outwardly the fingers 8 turn on their pivot in the upper contact block under the pressure of their spring until they engage the outer portion of the block. The upper end of the arm 6 then breaks contact with the plate 8b drawing an arc at the separation of the contacts. This arc is forced upwardly by the magnetic blow-out and as the arc becomes attenuated, it is forced upwardly to extend between the contact plate 6b and the contact plate 'Id where it is finally interrupted and quenched and the gases cooled by the auxiliary means to be described.

Each pole of the breaker is separated from its adjacent pole and enclosed within molded barriers of insulating material whereby each pole is enclosed within an insulating chamber. This eliminates the danger of fiash over between poles which otherwise might be caused by the flare of ionized gases during interruption. Furthermore the gases are forced outwardly through a quenching chamber where they are cooled before passing from the top of the breaker. The insulating barriers or partitions on each side of each pole are each made up of two separate portions. One portion I 3 is of general triangular shape and forms the rear lower portion of each partition. It backs against the lower portion of the panel I, being secured thereto by screws I3a, as shown in Fig. 2. The top of this portion of the partition extends forwardly from the panel I on a horizontal line I 3b close to the contact shaft 4 and then circles half-way around the rear lower portion of this shaft and then extends diagonally downward as shown by the line I3c in Fig. 2 close to the trip shaft I4, passing halfway around the lower inner side of this shaft and then extends downwardly at the surface I3d to an insulating plate I5 across the bottom of the breaker. This plate is secured to the lower enlarged edge I3e of the partition I3 by screws I3f. The other portion I6 of the insulating partition engages the portion I3 already described with an overlapping joint and butts against the upper portion of the panel I. It is secured to the panel by an upper row of screw bolts Ita and a lower row of screw bolts Ib. The corner screw bolts I6a also pass through the enclosing metal casing 2 and serve to hold the latter in place while the intermediate screw bolts Ia pass through a front insulating plate il within the front portion of the casing 2 and serve to hold this plate in place against the front vertical edges of the partition portions I5. The screw bolts iSd are tapped into a metal strip I8 across the topl of the rear ofthe panel. The screw bolts itl) are centrally located and pass through the iront insulating plate Il and through the partitions i and panel I and engage nuts Iiic at the rear of the panel; At the lower corners of the breaker screws I 6d pass through the casing 2 and er1- gage inserts in the lower ends of the partition portions I. Screws Iid between the lower corner screws pass through the plate Il and engage inserts in the lower ends of the intermediate partition portions I 5. The barrier partitions, front insulating plate il, lower insulating plate I5 and the casing 2 thus are held lirrnly in xed position.

The rear of the portions It extends from the top of the panel I down to the lines i3?) of the panel portions i3 and then extend forwardly and circles around the upper and front portions of the shaft I and then extends diagonally downward along the line ISC to the trip shaft It and circles around the front and upper portions of this shaft to the line i3d and then engages the lower insulating plate I5. The insulating disks or shields 5o on the shaft Il are positioned to engage the sides of the two portions I3 and i5 where they encircle the shaft 4 for the purpose of closing the spaces around the shaft and thereby isolating the metal parts of each pole of the breaker from other poles. Similarly the trip shaft I is provided with insulating disks Ia for closing the` spaces around this shaft where the barrier parti.- tions encircle the shaft. The top and front edges of the barrier portions it are wider than other parts thereof, as well as the central longitudinal portion through which the screws Ib pass. The upper parts of the barriers l form enclosed vertical spaces ide for separately enclosing the blowout coils l2, as shown in Fig. l. On each side of the vertical spaces ie are plates If of insulating arcresisting material which are secured to the sides at the top, front and mid portions of the molded insulation forming the barriers I 5. The openings ite extend to the panel l which permit the barriers I6 to be moved into position from the front of the breaker during assembly envelop the blow-out coils i2, slots being provided at one side in the plates Itf at the rear to permit passing beyond the leads I2a and i222 of the coils.

On each pole of the breaker is a chute for quenching the arcs formed when the breaker is opened and for cooling the gases before they pass from the breaker. These chutes are formed of side plates 23 of insulating material small front plates vila and rear plates 26h at the top of the chutes where they extend above the casing of the breaker, shown in Figs. l and 2. The plates .2li are provided with projections 2te on each side which extend longitudinally from front to rear and engage slots in the sides of the par- 'tions i6 abovethe plates If for retaining the chutes in position. AIn assembling the parts, the chutes are slid in from the front of the breaker and are retained in position by the front insulating plate Il. The chutes extend downwardly at the front of the breaker, as shown in Fig. 2, and

thus approach close to the region Where the arcsy are formed between the breaker contacts. Between the plates 20 extend a number of pins 20d of insulating arc-resisting material and are positioned in staggered relation, as shown in Fig. 2. When the arcs are forced upwardly from the contacts of the breaker, they strike these insulating pins which serve to quench the arcs quickly and to cool the gases as they pass upwardly and out through the chutes.

The operating mechanism of the breaker is enclosed within a space between two of the barrier partitions. It is supported by a U-shaped sheet metal frame 2I with the base of the U secured to the panel I by screw bolts 2Ia. The two sides of the frame extend forwardly from the panel and are provided with downwardly extending legs 2 ib. Fig. 5 shows the position of the parts when the breaker is open and in condition to be closed by the downward movement of the closing element or handle. Fig. 3 shows the parts when the breaker is closed and Fig. 4 shows the parts when the breaker has been tripped to open position. The main closing element of the breaker is the hand lever 22 which is pivoted on the pin 22a which is supported by the two sides of the frame 2i. This closing element extends forwardly through vertical slots in the insulating plate I1 and in the front portion of the casing 2 for permitting upward and downward movement of the hand lever. The rear end 22o of the main closing lever extends downwardly from the pin 22a and is pivotally connected to a pair of links 23 forming a toggle therewith. The links 23 are pivotally connected to a pair of links 24 which in turn are pivotally connected by a pin 24a to an arm 25 which embraces the insulation 5 on the contact shaft 4 and is clamped thereto. The ends of the pins 24a project into circular slots Zic in the sides of the frame 2 I. The upper ends of these slots serve as stops to limit the open position of the breaker. The links 24 and arm 25 serve to transmit the closing force from the handle 22 and the closing toggle to the shaft 4 and thereby move the contact arms 6 from their open position to their closed position by a downward movement of the handle 22. The pin 26 which pivotally connects the links 23 and 24 is supported and guided by the upper ends of a pair of guide links 2l which extend forwardly and downwardly, as shown in Fig. 5. Their lower ends are pivotally connected by a pin 28 to a pair of links 29, the inner ends of which are pivn oted on a xed pivot pin 3G which is supported by the two sides of the frame 2i. The pin 28 is normally restrained in xed position by a latch 3l, the lower end of which is xed to the trip shaft le. This shaft extends across the front of the breaker near the base, as shown in Figs. 1 and 2 and is journaled at its ends in the metal plates S. It is likewise journaled in the lower ends 2lb of the mechanism frame as shown in 5. Between its end journals and the part where it is journaled in the mechanism frame, this shaft is square in section, as shown in Fig. 2, and enveloped by a covering Ido of insulating material. Considering the parts in the positions shown in Fig. 5 with the pin 23 restrained by the latch, it is evident that when the closing arm 22 is depressed, it will tend to straighten the toggle 22h, 23 and force the pin 25 downwardly which in turn will force the links 24 downwardly and rotate the arm 25 in a clockwise direction and thereby move the shaft 4 and contact arms 6 to the closed position shown in Fig. 2. During this closing movement the pin 23 is guided by the links 21 in the arc of a circle about the pin 28 as a center. During this movement and also when the breaker is closed, the guide links 21 are under tension and endeavor to pull the pin 28 upwardly about the pivot 33 as a center; but cannot do this because the pin 28 is restrained by the latch. in the closed position of the parts, as shown in Fig. 3, the toggle 22o, 23 is overset and the closing handle will then remain in its lowest position.

When the latch 3| is moved outwardly to release the pin 23, the latter is thrown upwardly about the pivot 38 by the pull of the links 21 imposed by the pin 23. The contact arm 25 and links 24 then move upward rapidly from the position shown in Fig. 3 to the position shown in Fig. 4 whereby the contact arms 6 are rapidly moved to their open position. This rapid movement is due not only to the pressure of the contacts tending to move the arms 6 outwardly but is also due to the pull of a pair of springs 32 which are connected between a lower extension of the clamp of the arm 25 and projections 32a from the support 2 i. During this opening movement of the parts, the closing arm 22 remains in its lowest position, as shown in Fig. 4, the linkage connections permitting opening of the contact arms 6 without ailecting the movement of the closing element.

The breaker cannot be reclosed without first raising the handle 22 to its upper position. The raising of the handle swings the linkage to the position in Fig. at which time the Din 28 is engaged by the latch 3| and the mechanism is then in condition to reclose the breaker by a downward movement of the main closing element 22 in the manner already described. The open or closed position of the breaker is shown by a circular indicating plate 33 carried on the periphery of a plate 33a pivoted on a pin 33D which is supported by one side of the frame 2|. Pivotally connected to the disk 33a above its pivot is a link 34 which is pivotally connected at its rear end to a pin extending from the side of a clamp which holds the arm in position on the contact shaft. Openings through the casing 2 and insulating plate |1 permit an upper or lower portion of the indicating plate 33 to be exposed and visible from the outside of the breaker. When the breaker is open the lower part of the plate 33 is exposed and will show off or other designation through the opening; and when the breaker is closed it is evident that the indicator will be moved to expose its upper portion which may be marked on or otherwise designated to indicate a closed condition of the breaker.

The latch 3| is normally biased to engage the pin 23 by a spring 35 which is secured at one end to the pin and at its other end to a strip of meta-l 33 which is riveted or otherwise secured to the lower portion of the latch 3|. This latch is adapted to be tripped automatically by the overload magnet in a manner to be described later but it is also adapted to be tripped by the movement of the closing element 22 in a direction that would tend to open the breaker. For this purpose a lever having a downwardly extending arm 31 and a rearwardly extending arm 33 is pivoted to one side of the frame 2| at the elbow of the lever. A spring 39 is fixed at one end to a pin 40 which extends between the two sides of the frame 2| and serves as a stop for the closing arm 22 in its lowest position. The lower end of the spring 39 is secured to the arm 38 and tends to move this arm upwardly about its pivot. It also tends to move the arm 31 toward and against the pin 33. The upper end of the metal strip 36 is provided with a sidewise end projection 36a as shown in Fig. l, which is in the path of the lower end of the arm 31v When the lower end of this arm is moved toward the front of the breaker against the pressure oi the spring 31 it engages the projection 36a and forces the latch outwardly to release the pin 28. This action is accomplished by a tumbler element 4| which is pivotally mounted on an extension of the pin which connects the arm 22h with the links 23. The tumbler 4| is provided with a downward extension carrying a side pin 4|a which is positioned above and in the plane of the arm 38. The tumbler is also provided with two upwardly extending tongues Mb and 4|c which are spaced apart 'from each other. A pin 42 extends outwardly from the side of the arm 22D and is positioned between the two tongues of the tumbler and is adapted to be engaged by one or the other of these tongues. A spring 43 encircles the pin of the tumbler and has one end extended to engage the side of pin Ma of the tumbler and the other end extended to engage the front side of the pin 42. This spring consequently tends to keep the tongue 4|c of the tumbler in engagement with the pin 42, as shown in Figs. 3, 4 and 5.

In the upper position of the closing element 22 shown in Fig. 5, the pin 4|@ is out of engagement with the upper edge of the arm 33; and in the lowest position of the closing element 22 the pin dla is out of engagement with the arm 33, as shown in Figs. 3 and 4. The spring 39, under these conditions, causes the rear edge of the arm 31 to engage a sleeve on the pin 30 which serves as a stop for the arm. When the breaker is to be closed by a downward movement of the closing element 32 from the position shown in Fig. 5, the pin 4|a will be brought into engagement with the upper edge of the arm 38 and will follow the contour of this upper edge during the closing movement. This action would tend to depress the arm 33 and cause the lower end of the arm 31 to push against the side projection 36a of the strip 36 and release the latch from the pin 28 except for the fact that the tumbler spring 43 is sufficiently weak to permit the tumbler to rotate in a clockwise direction on its pivot and cause the tongue 4|b to approach the pin 42. This yieldability of the tumbler in the closing movement of the breaker thus avoids the depressing of the arm 38 and avoids releasing the latch 3|. When, however, the closing element 22 is moved upwardly from the position shown in Fig. 3 to open the breaker manually, the pin 4|@ is brought into engagement with the inner upper end of the arm 38 and owing to the fact that the tumbler cannot move in a counter-clockwise direction by reason of the tongue 4|c engaging the pin 42, the lower end of the tumbler will force the arm 3S downwardly and cause the arm 31 to force the strip 36 and latch 3| outwardly to release the pin 28. It therefore results that the breaker is quickly opened by the release of the latch upon the initial movement of the closing element 22 in a reverse direction to open the breaker. This prevents the breaker from being opened by a, slow separation of the contacts when the breaker is opened manually. Similarly during the closing movement of the breaker from the position shown in Fig. 5, on any reverse movement of the closing element 32, the tumbler will be caused to rotate on its pivot in a counter-clockwise direction and bring the tongue lo against the p-in 42. This action then results in the arm 38 being depressed and the latch l released permitting the parts be quickly thrown to open position by the pull of the springs 32. Thus a reverse movement of the closing element during any portion of the closing stroke will cause the parts to be automatically and rapidly thrown to open position which protects the contacts from the effects of arcing due to a slow separation of the contacts.

The breaker may be opened automatically upon the occurrence of any abnormal condition. In the present case an overload coil l I, already described, is provided for each pole of the magnet. It is positioned below each of the contact arms 6, as shown in Figs. 1 and 2. The overload assembly is shown in Figs. 2 and 6. It comprises a U-shaped supporting frame 44, the base of the U being secured to the panel l and the arms of the U embracing and supporting an iron or steel frame 45. IThis frame extends forwardly from the rear end of the overload coil and turns upwardly at the iront end of the coil. An iron or steel core 45 is enveloped by an insulating bushing 45a and is located within the overload coil, being supported at its front end by the upturned end of the core 45, as shown in Fig. 6.

The upper portion of this core is slotted to receive a freely movable push pin 4l. Opposite the end of each of these pins of the three overload coils is an arm 48 of sheet metal with outwardly turned edges and these arms are fixed to the common trip shaft I4, being mounted on the outside of the insulation |45. When any one of the push pins 41 is forced outwardly, it will engage its arm 48 and turn the trip shaft to release the latch 3l and thereby cause the automatic opening of the breaker in the manner already described. An iron or steel armature 49 of each overload coil is pivotally mounted on a pin 49a which extends between the two sides of the frame 44. This armature has secured to its rear side a sheet metal strip 55 which extends around the lower end oi the armature to a point below the end of the armature 49 and then is bent at right-angles and extends downwardly. A spring 5l is secured to the lower end of the strip 50 and is also secured to a projection 44a which is an extension from one side of the frame 44. It is evident that this spring tends to hold the armature 49 away from the core 46 of the overload magnet.

A thermostatic control is incorporated with the magnet for the purpose of tripping the circuit breaker after a time interval, depending upon the duration and amount of the overload current. This is in the form of a bi-metallic strip 52 which is secured to the front face of the frame 45 and extends downwardly and then along the underside of the magnetic frame 45 and between this frame and the corner of the metal strip 50. The end of the bi-metallic strip 52 thus serves to adjust the armature 49 and acts as a stop for the armature in its unattracted position. The positioning of the thermostatic strip 52 close to the magnetic frame causes its temperature to change and approximately correspond with the heating of the overload coil as ras.

determined by the value of the current passing through the circuit breaker. Under normal loads, or less than normal loads, the rise in temperature of the overload magnet is not suflicient to affect materially the thermostatic strip; but upon the occurrence of moderate overloads, the heating of the overload coil and the magnet frame is transferred to the thermostatic strip, and owing to its being composed of two metal strips having different coeflicients of expansion, causes the inner end of the bi-metallic strip to move downwardly to an amount depending upon the temperature rise. This action turns the armature 49 on its pivot to a greater or lesser extent against `the action of the spring 5| and moves the armature correspondingly closer to the core The closer the armature is brought to the core, the lower the value of the current in the overload coil Il which will attract the armature.

Assuming the circuit breaker to be closed, the automatic opening may be effected instantaneously upon the occurrence of an excessive overload because the current in the overload winding Il will then be so high that the armature 49 will be instantly attracted even though the armature 49 is in its outermost position from the core 45. This will drive the pin 41 against the arm 48 of the trip shaft and release the latch 3| and thereby cause the automatic opening of the breaker. Upon the occurrence of a moderate overload the rst effect is to cause the heating of the magnet which results in the thermostatic strip gradually adjusting the armature 49 closer to its core until a position is reached where the value of the overload current is surcient to suddenly attract the armature and shift the push pin 41 to trip the latch. It is apparent that the time of response of the breaker to an overload current depends upon the value of the overload current and the time interval of its continuance. It will also be appreciated that by providing an overload coil for each pole, the breaker will be tripped and all three sets of contacts opened upon the occurrence of an overload current in any one of the circuits which is sufficient in value and duration to cause the release of the latch.

Fig. 7 shows a modiiied form where an expansible thermostatic element is provided instead of a bi-metallic strip. Here the magnet frame 45a is extended to embrace both ends of the coil Il. A short iron or steel core 53 is xed to one end of the frame and extends a short distance within the coil Il. A movable magnetic core 54 passes freely through the frame at the other end of the coil. It carries a brass pin 54a which passes freely through the core 53 and is adapted to engage the arm 48 and trip the breaker when the plunger core 54 is attracted within the coil Il. A sealed expansible bellows 55 is secured at one end to the outer end of the plunger 54. The other end of the bellows carries a flange 55a. Between this flange and the end of the magnet frame and encircling the bellows is a spring 55 which tends to hold the plunger and bellows in their outer position, the end of the bellows seating against an upward extension of the frame 44. Within the sealed bellows is a liquid having a high coefficient of expansion, or a volatile liquid, which causes the bellows to expand longitudinally with increase in temperature. This bellows, like the thermostatic strip 52 is in juxtaposition to the magnet so that the heating thereof will correspondingly heat the bellows.

Upon the occurrence of an excessive overload,

the plunger 54 will be attracted within the coil l I instantly against the pressure of the spring 5B and cause the immediate tripping of the breaker. Upon the occurrence of moderate overloads, the magnet and bellows will be heated gradually and cause the gradual expansion of the bellows. This moves the plunger closer to the core 53 until a position is reached where the overload current will suddenly attract the plunger and trip the breaker. The time delay before this action occurs depends upon the amount and duration cr the overload. Under normal loads the heating is not suflicient to affect the position of the plunger materially and under such conditions the breaker is not tripped.

It will be understood that various modifications inay be made to fulfill particular requirements and to suit the preference of the designer without departing from the scope of the invention. The breaker may be provided with one,

two or more poles and adapted to be tripped by `a shunt tripping coil, under voltage control, auxiliary switch control, as well as the overload ccntrol. Instead of being hand operated, the 'breaker may be arranged to operate electrically :and may be arranged for front or rear switch- .board mounting. The foregoing description and .accompanying drawings illustrate a preferred ernlbodiment of the invention.

I claim:

l. In an automatic electric circuit breaker 'having a plurality of poles with relatively mov- :able contacts and having a common shaft for :actuating the movable contacts, a rear insulating supporting panel, and an insulating partition fextending forwardly from said panel between the poles and their contacts, said 'partition being formed in sections, one of said sections being :secured to said panel and partly encircling the shaft on one side thereof and the other of said sections being secured to said panel and partly encircling the shaft on the other side thereof.

2. In an automatic electric circuit breaker having a plurality of poles with relatively movable contacts and having a common shaft for actuating the movable contacts, a rear insulating supporting panel, an insulating partition extending forwardly from said panel between the poles and their contacts, said partition being formed ing disks carried by the shaft and positioned opposite the portions of said sections where they encircle the shaft.

3. In an automatic electric circuit breaker having a plurality of poles with relatively movable contacts and having a common shaft for actuating the movable contacts, a rear insulating supporting panel, and an insulating partition extending forwardly from said panel between the poles and their contacts, said partition being formed in sections, one of said sections beiner secured to a lower portion of said panel and partly encircling the shaft on one side thereof and the other of said sections being secured to an upper portion of said panel and partly encircling the shaft on the other side thereof.

4. In an automatic electric circuit breaker having a plurality of poles with relatively movable contacts and having a common shaft for actuating the movable contacts, a rear insulating supporting panel, an insulating partition extending forwardly from said panel between the poles and their contacts, said partition being formed in sections, one cf said sections being secured to a lower portion of said panel and partly encircling the shaft on one side thereof and the other of said sections being secured to an upper porin sections, one of said sections being secured ffii to said panel and partly encircling the shaft on one side thereof and the other of said sections being secured to said panel and partly encircling the shaft on the other side thereof, and insulattion of said panel and partly encircling the shaft on the other side thereof, an insulating cover plate secured to the bottom of said first named section, and an insulating cover plate secured to the front of said second named section.

5. In an automatic electric circuit breaker having relatively movable contacts, a rear insulating supporting panel, insulating partitions on opposite sides of said contacts and extending forwardly from said panel, a front insulating plate secured to said partitions and closing the front space between the partitions, and an are chute positioned between the upper portions of said partitions and removably supported thereby and retained in position by said front plate.

6. In an automatic electric circuit breaker having relatively movable contacts and having a vertically disposed blow-out coil at one side of and opposite said contacts, a rear insulating supporting panel, vertically extending insulating partitions on opposite sides of the contacts, one of said partitions having the blow-out coil enclosed within it, and an arc chute positioned between the upper portions of said partitions and supported thereby.

GEORGE A. HEALIS.

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