US2215792A - Circuit breaker - Google Patents

Description

sept 24, 1940- o. s. JENNINGs 2,215,792

CIRCUIT BREAKAER s sheets-smelt 1 Filed sept. 1o, 1937 lNyENToR Olive/"S Jennings.

BY zum 'A ATToRN WITNESSES:

`jJm

O. S; JENNINGS cIRcUT BREAKER Filed sept. 10, 1937 3 Sheets-Sheet 2 INVNTOR Oliver 5T .fen/227295. x BM d ATToR Y Sept. 24, 1940.

WITNESSES:

Patented sept. 24, 1940 UNITED STATES CIRCUIT BREAKER Oliver S. Jennings, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a. corporation of Pennsylvania Application September 10, 1937, SerialNo. 163,212

Claims.

The invention relates in general to circuit breakers and is particularly concerned with circuit breakers of the type used for controlling lighting and moderate power distribution feeder 5 circuits.

An objectv of the invention is the provision of an improved circuit breaker which is operable to automatically open the `circuit in response to an overload or abnormal condition and which will automatically reclose itself when, and only when, the condition causing the overload is removed or cleared from the controlled circuit.

Another object of the invention is theI provision of a circuit breaker of the type mentioned which is simple and inexpensive to manufacture and which is .safe and reliable in operation.

Another object of the invention is the provision of a circuit breaker of the above-mentioned type that is both manually operable and automatically operable to open and reclose the circuit.

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

Figure 1 is a vertical sectional view o f an automatic circuit breaker embodying the features of the invention, the various parts being shown in the positions they occupy when the breaker is closed; 35 Fig. 2 is a vertical sectional view of the circuit breaker, similar to Fig. 1, showing the parts in tripped open position following the occurrence of an overload of predetermined magnitude and duration;

Fig. 3 is a vertical sectional view of the circuit breaker, similar to Fig. 2, showing the position of the parts in the tripped open position following the occurrence of an overload, the latch means being shown in the operative position in which it prevents reclosing of the breaker;

Fig. 4 isa horizontal sectional view'of the circuit breaker shown in Fig. 1, taken on the line IV-IV of Fig. yl;

Fig. 5 is a schematic diagram illustrating the circuit which it controls;

Fig. 6 is a vertical sectional view of a modified form'of automatic circuit'breaker which includes means 'for manually opening and closing the contacts of the breaker;

electrical connection of the circuit breaker in the (Cl. F75- 294) Fig. 7 is a horizontal sectional view of the circuit breaker shown in Fig. 6, taken on the line VII- VU of Fig. 6, the electromagnetic latch means being omitted in order to simplify the -fgure; and

Fig. 8 is a schematic diagram illustrating a In the present invention, however, there is provided .in cooperative association with the breaker a novel means for preventing reclosing of the contacts of the breaker during the existence of the .condition causing the overload.

Referring to Figs. 1 through 5, inclusive, the single-pole double-break circuit breaker illustrated comprises in general a recessed base 9, a pair ofA spaced stationary contacts I'I, a. pair of cooperating movable contacts I3, an actuating mechanism indicated generally at I5 which is operable in response to predetermined overload conditions to move the contacts I3 to open circuit position, and which is automatically operable after a predetermined time to return the movable contacts I3 to closed circuit position, and a means indicated generally at I1 for preventing reclosing of the contacts during the existence of the condition causing the overload.

The various parts of the circuit breaker are supported and enclosed by the base 9, which is of molded insulating material, and if desired, a cover I9, also of'molded insulating material, may be provided for closing the open side ofthe base.

Two strips of conducting material 2| aresupported on the base 9 by means of screws 23. -A portion of each of these strips extends through the upstanding end wall of the base 9 in order to provide terminals for the breaker, suitable screws 25 being provided for connecting the line and load conductors thereto. The stationary contacts II are aiiixed to the inner ends of each of these conducting strips 2ly by means of the screws 23.

The two movable contacts I3 are c arried by a switch member consisting of a pair of U-Shaped bimetallic control elements 21. Each of the bi metallic control elements 21 comprises a substantially ilat strip of bimetallic material which- -ments 21. The ends of the control ,elements opposite tothe ends whereon the contacts lI3 are supported are electrically and mechanically connected by means of a tie member 3 I which comprises a fiat strip of conducting material riveted to the ends ofthe elements 21. A The interconnected control elements 21 are pivotally supported upon two spaced upstanding members 33 of insulating material, each of which is provided with a suitable bearing portion for engaging one of the pivot pins 29 of the control elements 21. The support members 33 are secured to the base by means of suitable screws 3l.

The bimetallic control elements 21 constitute a part of the actuating means of the circuit breaker which will now be described. 4In addition to the bimetallic control elements 21, the actuating means of the breaker includes a U-shaped pivot actuating member 31 and a pair of overcenter springs 39 which connect the free end of the actuating member 31 to the tie member- 3I"of the bimetallic control elements. The actuating member'31 is substantially U-shaped and ispivotally supported on a U-shaped support 4I secured to the base by means of screws 43. The pivot ends of the actuating member 31 are provided with bearing portions 45 (Fig. 4) for envsprings 39.'

gaging the pivot pins 41 carried by the support 4I. The tie member 3i and the cross portion 49 of the actuating member 31 are provided with openings which are engaged by the'bent ends of the overcenter springs 39.

A bracket member 5I, which is fastened to the base 9 by suitable means, is provided for defining the limits of motion of the actuatingmember 31,' these limits being adjustable by means of set screws 53 and 55. The limit of motion of the switch member consisting of the control elements 21 in a counter-clockwise direction about their pivot pins 29 is defined by the engagement'of the moving contacts I3 with the stationary contacts II, and the movement of the switch member in a clockwise direction is dened bythe engagement of the upper side of the contact end of each of the bimetallic elements 21 with a projection 51 that extends inwardly from the end wall `of the base 9.

through the tie member 3|, which connects the ends of the looped control elements, through the other looped control e1ement.21`v and its associated movable contact I3 to the opposite stationary contact Il and thence through the second conductingstrip 2l to the load.

It will be noted, as shown particularly in Fig. 4, that the space between the two bimetallic control elements 21 is entirely clear in orderto permit free motion of the overcenter operating Th circuit breaker. thus fardescribed is substantially the same as the automatic circuit breaker disclosed in the aforementioned Patent No. 2,070,305. 'Ihe operation of --the breaker as n thus' far described is briefly as follows: When thebreaker is in closed position, as shown in Fig.

1, and. an overload of suillcient magnitude and duration occurs in the circuit controlled by the.

breaker, the bimetallic -control elements ,21 are heated suillciently to move the tie member 3| in an upward direction away from thestationary contacts II. So long as thismovement does not bring the line of action of the overcenter springs 39 above the pivot axis 41 of the actuating member 3'1, the breaker will remain in closed circuit position. If, however, the overload is of suillcient magnitude and duration to cause the tie member to be moved a sumcient amount to change the line of action of the springs 39 relative to the pivot axis 41, it is apparent that the circuit breaker is in an unstable mposition due to the fact4 that the overcenter moves the line of action of the overcenter springsv 39 above the pivot axis 29 of the switch member consisting of the control elements 21, thereby producing a component of force tending to move -these elements in a clockwise direction about their pivot. This results in the movement of the control elements 21 and the movable contacts carried thereby from the closed' position shown in Fig. 1 to the open position shown in Fig. 2 with a snap action.

In the absence of the means for preventing reclosing of the breaker, the actuating means automatically recloses the contacts in the following manner. 21 have cooled, these elements assume their normal condition shown in Fig. l causing the tie member 3| to be moved downwardly. The downward movement of the tie member 3l -moves the line of action of overcenter springs 39 below the pivot axis 29 to eiect movement of the control elements 21 and movable contacts I3 from openy After the-bimetallic control elements` to closed position with a snap action. The movement of the control elements 21 to closed position moves the line of action of the overcenter springs 39 below the pivot axis 41 of the actuating member, so that the springs effect clockwise movementof the actuating member 31 from the position shown in Fig. 2 vback to the position shown in Fig. 1.`

In the above description of the operation of the breaker, it has been assumed that the move. ment of the bimetallic control Aelements 21 occurred in-response to internal heating produced by the flow therethrough of an overload current.

It is quite possible, however, to cause automatic operation of the breaker to take place as a result of changes in the temperature of themedium surrounding the breaker. Thus if the circuit breaker is disposed .within a transformer tank in such a manner that the bimetallic control elements are in contact with the oil used for insulating the transformer, 'the operation of the circuit breaker might result from a steady increase in the temperature of theoil. If the operation of the circuit breaker is affected by the heating ofthe surrounding medium, the breaker will in most instances'I remain in open .position for a considerable Vperiod of time due to the fact that the cooling of the large body of oil within the transformer tank takes place comparatively slowly.

Referring now to the means indicated generally at I1 for preventing reclosing of the circuit breaker during the existence of the condition causing the overload. This means comprises in.

general a pivoted latch 59 of magnetic-material or at least having a portion of magnetic material to form an armature, an electromagnet 6| for moving the latch from released position to latching position when energized a predetermined amount, and a transformer 63 for energizing the electromagnet 6|. The latch 59 is pivotally supported by means of a pivot pin 65 projecting from the side wall of the base 9 and is biased to an inoperative released position by means of a coiled compression spring 61 a portion of which extends within a bore provided -in the core of the electromagnet 6| One end of the spring engages a projection provided on the latch 59, while the other endof the spring engages an adjusting screw-69 which serves as an adjusting means for adjusting the amount of current required to move the latch from released to latching position.

The electromagnet 6| comprises a core 1| and a winding 13. The electromagnet is supported by an angle bracket 15 of magnetic material which is secured to one of the side walls of the base 9. The horizontal portion11 of the bracket 15 serves to support a pair of spaced contacts 19 and 8|, which are insulated from the bracket 15 by means of insulating spacer plates 83. vThe contacts 19 and 9| are adapted to be bridged to complete a circuit for the winding 13 of the electromagnet 6| when the breaker is in open position, by means o'f a bridging plate 85 of ,conducting material which is secured to the tie member 3| and insulated therefrom by means of an insulating plate 81, the bridging plate being disposed between the ends of the springs 39, as best shown in Fig. 4.

The transformer 63 is mounted on the ba'se 9 on any suitable location, and comprises a core 89, a primary winding 9| and a secondary winding 93 (Fig. 5). The internal electrical connections of the electromagnet 6|, the contact means 19, 3|, 85 and the transformer 63 are illustrated in the schematic diagram shown in Fig. 5. 'Ihe primary winding 9| of the transformer 63 `is connected in shunt relation across the contacts of the breaker by means of conductors 95 and 91, one terminal of the winding 9|. being connected by the conductor 95 to the line conductor strip 2|, and the other terminal of the primary winding being connected by conductor 91 tothe load conductor strip 2|. One terminal of the secondary winding 93 of the transformer 63 is connected to one-end of the winding of the electrovmagnet 6| by means of a conductor 99, the opposite terminal of the winding' 93 being connected to the return wire IDI by means .of .a conductor |93. 'I'he opposite end of the winding 13 of the electromagnet 6| is electrically connected to the contact 8| by means of a conductor |05, while the other contact 19 carried by the bracket 15 is connected to the load conductor strip 2| by means of a conductor |01. It will thus be seen that -the primary winding 9| of the transformer 63 is shunted by the contact means of the breaker when the breaker is in closed circuit position, so that lthe transformer is substantially deenergized under these conditions. A.It will also be seen that the electromagnet 6|is adapted to ber automatically connected byv means of the contacts 19, 6|, 65 in series circuit with; the sec- 'ondary 93 of thev transformer 63 and directly across the load and in series therewith when the breaker is in open circuit position.

Theoperation of the means for preventing reclosing of the contacts of the breaker is brieiiy circuit" position.

as follows: .With the circuit breaker in closed position, as shown in Fig. 1, the transformer 63 is shunted by the breaker contacts, so that it is substantially deenergized and nol current ows through the electromagnet 6|. Thusthelatch 59 is maintained by the spring 81 in inoperative or released position. lWhen an overload in the circuit controlled by the breaker occurs, the switch member and movable contacts I3 are automatically moved to the open circuit position inthe manner previously described as a result of the flexing o'f the bimetallic control elements 21. When the movable contacts i3 separate from the stationary contacts and the arc is extinguished, current iiows through the primary of the transformer 63 since it is no longer shunted bythe contact means of 4the breaker. This materially reduces the flow of current to the load so as to protect the circuit and load apparatus. When the switch member and movable contacts I 3 have reached their full open circuit position, the bridging plate 85 bridges the stationary contacts 19 and 8| to complete a circuit for the electromagnet 5| which connects the electromagnet 6| in series circuit with the secondary-Winding 93 of the transformer B3 and the load. Since the transformer 63 is energized due to the opening of the main contacts of the breaker, the electromagnet`6| is now energized an amount depending upon the impedance of the load since it is in series therewith. If the impedance of the load is below a predetermined amount, that is to say,

if the condition causing the overload still exists,

the electromagnet 6i is energized a sufficientamount by the current flowing through its winding to move the latch from its inoperative or released position, as shown in Fig. 2, to latched position, as shown in Fig.3, in which it engages the tie member 3| connecting the bimetallic con-v trol elements 21 to hold `these elements in open Under these conditions, the switch member and the movable contacts I3 are held latched in open position to prevent reclosing ofv the circuit breaker. The circuit breakerA cannot be reclosedby the actua-ting mechanism until the impedance of the load is increased as by reducing the magnitude vof the load to a value substantially equal to or less than a safe normal full load value, or until the fault condition causing the overload is corrected or cleared. V When this is done, the pull of the electromagnet 6| is reduced because of the reduction in the current flowing through its winding so that .the force exerted by the biasing spring 61 is sumcient 'to move the latch to its inoperative or released position, as shown in Fig. 2 to release the switch member. I'he actuating mechanism is .now free to automatically reclose the circuit breaker.

When the latch 59 releases the tie member- 3|, the bimetallic control elements 21 which have cooled a sufficient amount, move the line of action of the overcenter springs 39 below the pivoted axis 29 of thevcontrol elements 21 to eil'ect automatic reclosing of the circuit breaker vin the v manner previously described. y

|The adjusting screw 69 .forms a simple adjusting means: for adjusting the amount of current required to cause the electromagnet to move the latch from inoperative to latching positiomso that the lock-out means |1 may be adjusted to operate under different predetermined circuit conditions.

The magnetic circuit of the electromagnet 6| is so designed that the latch I9 'will be moved to its in any number of ways, one way being to have a very small air gap between the armature portion of the'latch 59 and the core 1I of the' electromagnet.'

vA modification-of the invention is illustrated in' Figs. 6 and 7. The structure of the circuit breaker in this modiiication is substantially similar to the previously described circuit breaker and to the embodiment shown and described in connection with-Figs. 8 and 11 'of the aforementioned Patent No. 2,070,305. In this modification, the circuit breaker 'is provided with a manual operating means for opening and closing the breaker. Since the basic structure is substantially similar to the device previously described, the same reference characters will be lused wherever applicable.

The circuit breaker illustrated in Figs. 6 and '1 comprises in general a recessed base 9 of molded insulating material, a pair of stationary contacts II, a pair of cooperating movable contacts I3, an

actuating means indicated generally at I5, al

means indicated generally at I1 for preventing reclosing of the circuitbreaker during the existence of the condition causing an overload, and a manual operating means indicatedgenerally at The stationary contacts I I are secured to a pair of terminal conducting strips 2| which are .in turn secured to the base 9 by means of screws 23.

'I'he movable contacts I3 are carried by a switch member consisting oi a pair of U-shaped bimetallic control elements 21, the upper ends of which are mechanically and electrically connected together by means of a tie member 3| of conducting material. The control elements 21 are provided with pivot pins 29 for) pivotally mounting the elements on a pair of spaced supporting members`33 of insulating material.

The bimetallic control elements 21 form a part of the actuating means which will now be brieily described. The actuati'ng'means for the breaker includes the bimetallic control elements 21, a U- shaped actuating member 31 pivoted at 41 on a support 4|, al pair of overcenter springs 39 connecting the free end portion 490i the actuating member 31 to the tie member 3|.`

The movement of the switclimember consistl ing of the bimetallic control elements 21 and the movable contacts I3 in a clockwise direction about their pivot axis is limited by an inwardly extending projection'51 formed on the end wall of the base 9.

A bracket member 5| is provided for deiining the limits of movement ofthe actuating member 31,'these'limits being adjustable by means of set screws 53 and 55.

The means I1 for preventing reclosure of the circuit breakery is identical to the correspondingV means of the previously described device, andV comprises generally a pivoted magnetic latch 59 l biased to released or inoperative position by a spring 81, an electromagnet`6| for moving the latch from released to latching position when energized a predetermined amount, and a transformer indicated generally at 63 for energizing the electromagnet 6I. The electromagnet 9| is provided with an adjusting screw 69 which serves asan adjusting means for determining tire amount of vcurrent required to move the latch from inoperative to latched'position.Y A pair of stationary contacts 19 and gl are' supported by and closing the contacts of the breaker.

Vthe bracket which supports the electromagnet 6| and insulated therefrom by the insulating plates 93. These contacts 19 and 3| are adapted to be bridged by a bridging plate 85 of conducting material which is secured to the tie member 3| and insulated therefrom by an insulating platel A91.

' the contact means of the breaker.

In this modication of the invention, the circuit breaker is provided with a manual means indicated generally at |09 for manually opening The manual means |09 comprises in general a bifurcated operating member III which straddles the actuating mechanism and which is pivotally vsupported by means'of pivot pins ||3 on the support 4|, an operating handle II5 secured to the bight portion of the operating member III anda pair of depending projections ||1 and IIB formed integral with the bight portion of the operating member III. The handle ||5 projects through an opening I2 I provided therefor in the cover |23 of the base, and has-a closure portion which acts to close the opening in any position of the handle. Y

The actuating member 31 of the actuating means of the circuit breaker is provided with a Y- shaped coupling member |21, the legs of which are secured to the legs of the actuating member 31 by means of rivets |29 (Fig. '1). The upper end |3I of the VY-shaped coupling member |21 is disposed between the depending projections II1 and II8 'of the operating member III for engagement thereby when the operating handle II-5 is moved.

The ,spacing of the projections ||1 and IIB is such that they-permit the actuating member 31 to be movedY independently of the operating handle during automatic operation of the actuating means when the handle is in closed circuitv ber III of insulating material which extends 'I Athrough a slotted opening |43 in one of the side walls of the base 9. This member Ill permits the latching member |33 to be moved so as to disengagethe operating handle and permit manual operation of the breaker.A The latch |33 is biased by a spring I (Fig.y '7) towards latching position so as to latch the operating member II I when the same is moved to clo'sedcircult -V position.

The circuit breaker is -shown in the closed circuit position in Fig. 6. It will be noted that the latch |33 through engagement of the latch recess '.I31 with the pin .|39 holds the operating'member II in closed circuit position. If it is desired to manually open the breaker, Vthe latch |33 is lifted by means of the insulating projection III and the handle is moved in a counter-clockwise direction. During this movement, the projection |3| vof the coupling member |21 then disengages the projection H1 and moves with the actuating member 31 towhich it is secured, under the biasing vaction of the overcenter springs 39 to open circuit position. In moving to this position, the

line of action of the overcenter springs 39 is carried across and .above the pivot axis 29 of the bimetallic control elements 21, and these members together with the movable contacts carried thereby move to open circuit position with a snap action. s

In manually` closing the circuit breaker, substantially the reverse action takes place. TheA operating handle H5 is moved in a clockwise direction about its pivot H3 to close the contacts of the breaker. During this movement, the depending projection H8 engages the upper end |3| of the coupling member and moves that member together with the actuating member 31 to which it is secured in a clockwise direction about the pivot axis 41 to the closed circuit position shown in Fig. 6. During this movement, the upper end of the coupling member |21- disengages the projection H8, and the line of action of the overcenter springs irst crosses the pivot axis 29 of the bimetallic control elements to eiect movement of the control elements: 21 and the movable contacts I3 to closed circuit position with a snap action, and then crosses the pivot axis 41 Aof the actuating .member 31 to effect movement .of that member to closedposition shown in Fig. 6.

Both the opening and the closing operations once initiated by the operating handle take place substantially instantaneously and with increasing acceleration as soon as the line of action of the overcentersprings 39 crosseseither of the pivot axes 29 or 41. A

As has previously been pointed out, the spacing ofthe projections ||1 and ||8 is such as to permit automatic operation' of the actuating means I5` when the handle is held latched in closed position.

The automatic operation ofv the actuating means is identical to the automatic operation of' the device shown in'Figs. 1 to 4 and previously described in connection therewith. Briey,' when the breaker is in closed position, the handle being held latched inclosed position, as shown in Fig. 6, and a predeterminedv overload or increase in temperature of the ambient medium occurs, the bimetallic control elements 21 expand in such a manner thatthe tie member 3| is moved Vupwardly. A This upward movement of the tie member carries the line of action of the springs 39 above the pivot laxis 41 of the actuating member 31, and the springs will exert a component biasing that member in a counter-clockwise direction. The immediate result is to .cause the actuating member 31 to move in a counter-clockwise direction, the limit of motion being deilned by the engagement of the upper end |3| of the coupling member ,|21 with the depending projection H8 of the operating member IH. As the actuating member 31 moves'in a counter-clockwise direction, as described above, the line ot action of the springs 39 iscarried vacross and above the pivot axis 29 ofthe connected bimetallic control elements, thereby causing those elements and the movable contacts I3 carried thereby to be moved from closed to open circuit position with a snap action.

In the absence of the lock-out means I1, the actuating means eiects automatic reclosure of the contacts in the following manner: Asvthe bimetallic control elements 21 cool following automatic opening of the contacts, the tie member 3| and with it the line of action of the overcenter springs 39 is moved downwardly. As soon as the line of action of the springs crosses the lpivot axis 29 ofthe connected control elements,`

these elements and the movable contacts I3 carried thereby are moved to closed circuit position with a snap action. As f this movement prosprings 39 also crosses the pivot axis 41 of the actuating member 31 to cause clockwise movement of that member to the position shown in Fig. 6.

The depending projections H1 and H8, which provide opposed surfaces for engaging the coupling member |21, comprise in effect alost-motion connection between the operating handle and the actuating means. Thus, even though the handle is held in closed circuit position, as shown in Fig. 6, either manually or through the agency of the latch |33, the breaker will open4 automatically upon the occurrence of an overload. 'Ihe breaker is thus entirely trip-free of the operating handle.

'I'he latch controlling electromagnet 6I and the transformer 63 are electrically connected in the i same manner asin the embodiment shown in Figs. :1 through 5 and described in connection therewith. Theprimary of thev transformer 63 is connected in shunt relation to the main contacts of the breaker, and the secondary winding of the transformer yis connected lin series circuit With the electromagnet 6| and the load when the breaker is in open-'circuit position by means `of the contacts 19, 8|, 85, as previously described in connection with Fig. 5.v

' The operation of the lock-out means indicated generally at I1 is substantially'identical with the corresponding means described in connection with Figs. 1 through 5. The transformer 93 becomes energized when'the breaker opens, ,and the electromagnet 6| visconnected-in series circuit with the secondary of the transformer and with the load by the 'closing of the contact means 19, 8|, 85 `when the breaker reaches full-open circuitl position. Ifthe impedance of the load is -below a predetermined fvaluefthe current ow through the electromagnet is sufcient to move the latch 59 fromlnoperative to latched position, in which last position it latches the switch member consisting of the bimetallic control elements .21 and the movable contacts. I3 in open circuit position, so that the breaker cannot be reclosed until the fault condition is cleared-or the im pedance ofthe load is increased, as, for exam-- ple, by removal of part of the load apparatus from' the circuit, When the impedance of the load ycircuit is increased above the predetermined g5 value, or the fault condition is cleared, the pull of the electromagnet 9| becomes insuflicient to hold the latch 59 in its latching'position, and the spring 61 moves thelatch to its inoperative position, as 'shown in Fig. v6, to effect release of the 70 switch member. yFollowingrelease Vof the switch member, the actuating meansautomatlcally recloses the circuit breaker in a manner previously described.

s In order that the transformer 93 will not be u gresses, the lin e of action of the overcenter f 6 energized when the breaker is manually opened by means of the operating handle H5, a cut-out switch indicated generally at |41 is provided which opens the circuit to the primary of the transformer when the operating handle is moved to open position to open the breaker. The plunger |49 of the cut-out switch is moved downwardly to open the` switch by a projection ISI formed at the lower end oi' one of the legs of the operating member This projection III moves the plunger |49 downwardly to open the switch |41 when the operating handle IIS is moved to open position. The contact means of the cut-out switch |41 are adapted to be'connected in the conductor leading to the primary 9| of the transformer, as indicatedby the alternative dotted lines |53 in Fig. 5.

A further modification of the invention vis illus-V trated schematically in Fig. 8. In this modiilcation, the circuit breaker' and ltsactuating means are identical' to that shown and described in connection with Figs. 1 through 4. The breaker operates automatically in the same manner as.

impedance |6| is connected in shunt circuit relationship to the contact means of the breaker and a resistance |93 is connected in series circuit with the latch controlling electromagnet 6|. It will be noted that when the circuit breaker is in open circuit position, the contacts 19, 85, which mayA take'the form of the contact means 19, 8|, 85

shown in Figs. 1 through 4, connect the electromagnet 6| in parallel with the load |65, the circuit for the electromagnet and the load circuit being connected in series with the impedance IBI.-

The operation of this modiilcation of the invention is brieily as follows: When the circuit breaker is'opened in response to predetermined overload conditions, the electromagnet is connected in parallel with the load by means of the contacts 19, 85. If the impedance` of the load is below a predetermined value, insumcient current will flow through the electromagnet 6| to move the latch to inoperative position, and the movable 'contacts will be held in open circuit lposition by means of the latch 59, so that the breaker is prevented from. being automatically reclosed. When the impedance of the load circuit is increased above the predetermined value, as by removing a part 'of the load from the circuit or by correcting the fault condition causing the overload, suicientV current will ilow through the electromagnet 6| to move the latch 59 to its inoperative or released position. The actuating means of the circuit breaker is now free to reclose the contacts of the breaker in the manner previously described in connection with the embodiment shown in Figs. 1 through 4.

It will thus be seen that the invention provides an improved automatically reclosing circuit breaker embodying a lnovel means for preventing reclosing of the contacts of 'thebreaker during theexistenc'e of the condition causing the overload, the means for preventing reclosing of the contacts being automatically rendered inoperative to prevent reclosure when the fault condition is cleared.

While the invention has been disclosed in accordance with the provisions of the statutes, it

is to be understood that various changs in the structural Adetails thereof may be made without departing fromv the spirit of the invention. It is desired, therefore, that the-appended claims be -given the broadest reasonable construction permissible in the light of the prior art.

Iclaimasmy invention: f, l.. In a circuit breaker for controlling a load circuit, relatively movable contacts, actuating means including an overcenter spring for opening and closing said contacts and an electro-responsive element operable in response to predetermined overload conditionsfto cause' said spring to automaticallyv open said Lcontacts and operable to cause said spring vto automatically reclose said lcontacts following automatic opening thereof,

means operable upon automatic openingof said contacts for preventing reclosing of said contacts during the existence of the condition causing the overload, said means comprising a latch normally biased to released position and movable to a latchlng position to hold said contacts open,

an electromagnet for moving said latch to latching position when -energized a predetermined amount, transformer the primary of which is connected in shunt relation tosaid contacts and -the secondary `of.which is conriected in series with said electromagnet, and means forfautomatlcally connecting said transformer secondary and said electromagnet in shunt relationto the load when said contacts are automatically opened, the magnetic circuit of said electromagnet being such that its reluctance is changed only a rela- )tively small `amount by the movement .of said Y latch to latching positioh so as to permitv return of said latch to released position when the currentilowing through said electromagnet is decreased to a value only 'slightly below the value required to cause said latch to be moved to latching position. A

2. In a circuit interrupter for controlling a load circuit, relatively movable contacts, an overcenter spring for opening and closing said contacts, an electro-responsive control element voperable in response to predetermined conditions to cause said spring to automatically open said contacts and for causing said spring to automatically reclose said contacts after ,an interval of time following said automatic opening operation, means operable upon automatic opening of said contacts for preventing reclosing of said contacts until the predetermined conditions haveceased l to exist, said means comprising a latch operable to latch said contacts open, and an electromagnet acting directly on said latch for controlling the latch, means electrically connecting said electromagnet in shunt relation to the load circuit when said contacts are automatically opened, and an impedance connected in shunt relation to said contacts, said electromagnet causing said latch to release said contacts for closing immediately upon cessation of said predetermined conditions. 4

3. In a circuit interrupter for controlling a load circuit, relatively `movable contacts, an overcenter spring forlopening and closing said contacts, an electro-responsive control element operable inresponse to predetermined conditions to cause said 8911113 to automatically open said contacts and for causing said spring to automatically re- I close said contacts after aninterval of time ioling its secondary connected in circuit'l with the lowing said automatic opening operation, means operable upon automatic opening of said contacts for preventing reclosing of said contacts during the existence of said predetermined conditions, said meanscomprising a latch yoperable to latch said contacts open, an electromagnet acting directly on said latch for'controlling said latch, means for automatically electrically connecting said electromagnet in shunt with the load upon automatic opening of said contacts, and an impedance connected in circuit with the load upon automatic opening of said contacts, said electrovat magnet causing said latch to free said contacts for closing immediately upon cessation of said predetermined conditions.

4.7In a circuit breaker for controlling a load circuit, relatively movable contacts, actuating means including an overcenter spring for opening and closing said contacts and an electro-responsive control element operable in response to predetermined overload conditions to' cause said spring to automatically open said contacts and for causing said spring to automatically reclose lsaid contacts after a time interval following said automatic opening operation, means operable upon automatic opening of said contacts for preventing reclosing of said contacts if the impedof the conditions causing the overload.

5. In a circuit breaker for controlling a load circuit, relatively movable contacts, actuating means including an overcenter spring for opening and closing said contacts and an electro-responsive control element operable in responsetofpredetermined overload conditions to cause said .spring to automatically open said contacts and for causing said spring to automatically reclose said contacts after a. time interval following said automatic opening operation, means operable upon automatic opening of said contacts for preventing reclosing of said contacts if the impedance ofthe load circuit is below a predetermined value, -said means comprising a latch operable tolatch said contacts open, an electromagnet for controlling said latch,'and a transformer the secondary of which is connected in circuit with said electromagnet and together with the electromag' net in shunt to the load upon automatic opening of saidcontacts, the primary'of said transformer being connected in'shunt to the contacts.

'6. In a circuit interrupter for controlling a load circuit, relatively movable contacts, an overcenter spring for opening and closingr lSaid. contacts.- an electro-responsive control element'operable in response to predetermined conditions to cause said lspring to automatically open said con- Y tacts and for causing said spring to automatically exist, said means comprising a latch operable reclose ,said contacts after an interval of time following said automatic opening operation.'

means operable upon 'automatic opening of said contacts'for preventing reclosingof said contacts.

until the predetermined conditions have ceased to to latch said contacts open, and an electromagnet for controlling the latch, and a transformer havelectromagnet and its primary connected in shunt relation to said contacts, the'secondary of the transformer and the connected electromagnet being connected in shunt to the load upon auto- 5 matic opening of said contacts.

7. In a: circuit breaker forcontrolling a load circuit, relatively movable contacts, actuating means including an overcenter spring for opening and closing said contacts, and an electro- 10 responsive control element operable in response to predetermined overloadl conditions to cause said spring to automatically open said contacts, and -for4 causing said spring. to automatically reclose said contacts after an interval of time fol- 15 lowing said automatic opening operation, means operable upon automatic opening of said contacts for preventing reclosing of said contacts during the existence of the condition vcausing thegoverload, said means comprising a latch operable to 20 latch said contacts open, an electromagnet acting directly on said latch for controlling said latch, means for automatically connecting said electromagnet in shunt`re1ation to the load when the contacts are automatically opened, andan 26 impedance connected in shunt relation to said contacts, said electromagnet being operable to cause said latch to release said contacts for reclosing immediately upon cessation of the condition causing said overload.

` 8. In a circuit breaker for controlling a load circuit, relatively movable contacts, actuating means including an overcenter spring for opening and closing said contacts and an electro-responsive element operable in response to predeter- 3/5, mined overload conditions to cause said spring to l' automatically open said contacts and operable to cause said spring to automatically reclose said contacts following automatic opening thereof, meansV operable upon automatic opening of said 40 contacts for preventing reclosing ofsaid contacts during the existence of the condition caus ing the overload, said means comprising a latch. normally biased to a released position and movable to a latching position to latch said contacts itiopen, an electromagnet for moving said latch to latching position when energized a predetermined amount, a transformer the primary of which is connected in shunt relation to said contacts and the secondary of which is connected in series with said electromagnet, means for automatically connecting said transformer secondary and said electromagnet in shunt relation to the load when said lcontacts are automatically opened, the magnetic circuit of said electromagnet being such that its reluctance is changed only a relatively small amount by the movement of said latch to latching position so as to permit returnof said latch to released position when the current flowing through said electromagnet is decreased to a. value only slightly below the value required to cause said latch to be moved to latchingposition,` and adjusting means for varying the value of current required to cause said electromagnetto move said latch to latchins position.

9. In a circuit breakerfrelatively movable contacts, actuating means automatically operablein response to predetermined conditions to open said l contacts and tothereafter reclose said contacts, a manual operating handle' movable to cause 70 opening or closing of said contacts, an impedc ance connected at all times in shunt relation to said oontactarmeans operable upon automatic opening of said contacts for preventing reclosing of said contacts as long as said predetermined condition exists, and means operable by opening movement o! the manual operating handle for opening the circuit to interrupt the flow of cur- 10. A circuit breaker for controlling a load circuit eomprising relatively movable contacts, actuating meansincluding an overcenter spring for opening and closing said contacts, an electro-responsive element operable to cause said spring to automatically open said contacts, in response to predetermined overload conditions and for causing v'said spring to automatically reclose said contacts after automatic opening thereof, a manually operable handle operable to open and to close said contacts, an impedance connected in shunt to said contacts, and electromagnetic means operable upon .automatic opening of said contacts to prevent reclosing of said contacts as long as the impedance of Athe load circuit is below a predetermined value, and anadditional pair of contacts in the circuit opened by opening movement `of said manual operating handle for interrupting l0 the flow of current in the circuit.

' OLIVER S. JENNINGS.

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