US2050284A

US2050284A - Circuit interrupter

Info

Publication number: US2050284A
Application number: US600660A
Authority: US
Inventors: Hiller D Dorfman
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1932-03-23
Filing date: 1932-03-23
Publication date: 1936-08-11
Anticipated expiration: 1953-08-11

Description

Aug. 11, 1936. H D. FMAN 2,050,284

CIRCUIT INTERRUPTER Filed March 23, 1932 5 Sheets-Sheet l a? Fi'gr INVENTOR I MHz/2P0," mar).

ATTORN Y Aug. 11,1936. DORFMAN 2,050,284-

I CIRCUIT INTERRUPTER Filed March 23, 19313 3 Sheets-Sheet 2 WiTNESSESi INVENTOR 5 Mme/ppm man. A v A BY k7: A

6 2. M 6/; r I I g r ATTORNEY Aug. 11, 1936. H. D. DORFMAN v CIRCUIT INTERRUPTER 3 Sheets-Sheet 3 Filed March 23, 1,932

i INVENTQR H/Y/rfi pay man WITNESSES: W

ATTORNEY UNITED, STATES PATENT OFFICE 2,050,284 CIRCUIT m'rsnanr'rna Hiller D. Dorfman, Mansfield, Ohio, assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application March 23, 1932, Serial No. 600,660 39 Claims. (Cl. 200-116) My invention relates to circuit breakers and particularly to circuit breakers of the type in which the breakeroperating means is manually operable to open or to close the circuit, and is automatically operable to open the circult and to prevent the closing of the circuit upon the occurrence of short circuit or overload con-' ditions.

One Object of my invention is to provide a circuit breaker havingan improved trip mechanism capable of opening the breaker in response to an overload condition in the controlled circuit, the trip mechanism being capable of distinguishing between overloads of differing magnitude and having means associated therewith for causing a time interval to elapse between the occurrence of an overload and the opening of the breaker, the time interval being inversely proportional to the magnitude of the overload current.

Another object of my invention is to simplify and improve the bimetallic thermally responsive elements used in circuit breaker trip mechanisms in order that those elements may be manufactured and operated more economically than has been heretofore possible. In carrying out this object, I provide bimetallic elements designed to give the maximum of deflections .with a minimum of mass and a minimum of heating. I am, thereby, able to reduce the manufacturing costs of these elements both by reducing the amount of bimetal required and by simplifying the design. In addition, by reducing the amount of heating required, I am able to reduce the resistance of the .element and thus reduce the normal operating losses of the breaker.

A further object of my invention is to provide a trip device for a circuit interrupter in which the thermally responsive elements shall be free from external stress.

A further object of my invention is to provide a trip mechanism for a multi-pole circuit breaker having a thermally responsive element associated with each pole thereof, and a means engageable and operable by any one of said thermally responsive elements to trip all of the poles of said breaker.

A still further object of my invention is to provide a trip mechanism for a circuit breaker which shall be capable of opening all of the poles of the breaker after a very short time delay upon the occurrence of a short circuit and after a predetermined longer t me interval upon the occurrence of an overload condition, which shall be capable of tripping the breaker irrespective of the position of the operating handle, and which shall be resettable to the operating position'by means associated with the operating handle.

The principal field for immediate application of my invention is in connection with multi-pole circuit breakers for controlling lighting and dis- 5 tribution feeder circuits, and I shall hereinafter describe an embodiment of my invention as applied to such circuit breakers without in any way intending to restrict my invention, except as indicated in the appended claims.

In this embodiment of my invention, I provide a plurality of switch members and a plurality of contact members for opening a plurality of poles. In addition, I provide a manually operable mechanism for moving the switch members to the open 15 andclosed positions with a snap action, an insulating base upon which the structure is assembled, an arc extinguishing device for each pole, a means for biasing each of the switch members to the open position,- a releasable restraining 20 means for holding all of the switch members closed, and a unitary trip device for releasing the restraining means in response to a predetermined electrical condition in any one pole and thereby opening all of the poles of the breaker, the re- 25 leasing means being operable to open the breaker regardless of the position of the operating handle.

The features of my invention which I believe to be new are particularly pointed out in the appended claims. For a full understanding of the 30 principles of the invention, reference may be had to the accompanying drawings, in which Figure 1 is a plan view of a two-pole circuit breaker embodying the principal elements of myinvention; the cover has been" removed and part 35 of the operating handle has been cut away to more clearly show the various parts of the operating mechanism; a

Fig. 2 is a plan view of the cover for the breaker shown in Fig. 1;

Fig. 3 is a sectional view on the line III-III of Fig. I;

Fig. 4 is a sectional view onthe line IV-IV of Fig. 3;

Figs. 5 and 6 are fragmentary views of the breaker operating mechanism; and Figs. 7 to 19,,inclusive, are enlarged detail views showing various modifications of the bimetallic thermally responsive elements used in this embodiment of my invention.

Referring particularly to Figs. 1, 3, and 4 of the drawings, the insulating base I is of molded insulating material-and has mounted thereon the contact terminals 3 and 5,the circuitbreaker operating mechanism I which has associated therewith the assemblage of the two switch members 5, the trip mechanism 9, the arc extinguishing structures i i, and the stationary contact assemblages. As will be more fully pointed out later, these various parts are all attached to the insulating base by means of suitable screws. The switch members 8 and the stationary contact assemblages combine to form the two poles of the breaker. An insulating barrier M which is molded in the base, serves to separate the two poles. An insulating cover 2 (Fig. 2) is provided which completely encloses the breaker operating mechanism and the tripping mechanism.

The electrical circuit for each pole of the breaker is substantially the same. Beginning with the terminal contact the current next flows through the stationarycontact assemblage comprising the conducting strip 83 and the stationary contact G5, the moving contact ii and the conducting shunt it of the switch member 5, the trip device 9, and the terminal contact 5.

Each of the switch members 5 has an iron frame 2| upon which the remainder of the structure is assembled. Fastened to the part of the frame 2| adjacent the base i, by means of the rivets 23, is a fiat spring 25; the moving contact i1 and one end of the shunt l9 are fastened to the free end of the flat spring 25, by means of the rivet 21, which extends through suitable openings in the conducting shunt i9 and the spring 25. The spring 25 provides a means for securing contact pressure between the contacts 5 and H, and, in addition, serves to bias the switch member 8 to the open position. Each of the switch member frames 2| has two projections 29 of reduced width which extend downwardly (Figs. 1 and 3) from the frame proper. These projections are provided to engage an insulating bar ill which extends across both of the poles. Suitable openings are provided in the insulating bar it for the reception of these projections 25; the projections being of sufficient length that they may be bent over and clinched after passing through the openings in the insulating bar 3|, and thus serve to securely fasten each of the frames 2| to the bar 3|. It will be noted that three switch member-frames 2| are provided, although there are only two switch members; the centrally disposed frame being utilized for engaging the circuit breaker operating mechanism. The insulating bar 3| provides a convenient means for operating both of the switch members 8 from the single operating mechanism I, and, in addition, it provides a means for interconnecting the switch members 8 so that both open and close together.

One end of each of the conducting strips I3 is fastened to a terminal contact 3 by means of a bolt 33 and its associated nut 34. The conducting strip itself is fastened to the insulating base by means of a screw 31 which engages a suitable threaded opening 38 therein. Each of the stationarycontacts I5 is fastened to its associated conducting strip I3 by means of a screw 39. I prefer to use are resistingmaterials for the stationary contacts l5 and the moving contacts ii, a mixture of silver and graphite being utilized for the former, and an alloy of silver and molybdenum for the latter.

The are extinguishers ii are of' the spacedplate type in 'which a plurality of plates of magnetic material, each insulated from the other and having slots therein, are provided.

These extinguishers are disposed adjacent to the arc path-the slots being of substantially the same outline as the moving contacts-and upon the establishment of the arc, the magnetic field around the arc is altered by the plates so as to force the arc to move into the spaces between the plates where it is quickly cooled and extinguished.

In the structure which I prefer to use, the ma,,- 5 netic plates 4|, having slots 42 therein, are as-, sembled between two end plates 43 of insulating material, projecting lugs (not shown) being provided in the magnetic plates 4| for engaging the end plates 43. In the assembled breaker structure, two insulating members 45 are provided. These insulating members 45 extend across the upper part (Fig. 1) of the open end of the are extinguishing structures It and engage the central insulating barrier i2 which separates the two poles of the breaker. They serve to more completely separate the arc chambers from the remainder of the structure, and give an increased margin of safety when interrupting heavy arc currents by assisting in preventing fiashovers between the adjacent poles.

The operating mechanism l comprises, in general, a U-shaped frame 4i, a pair of toggle links 49 and 5|, a trigger 69 for releasably restraining the toggle links 49 and 5| in the operative posi tion, a bifurcated operating lever 55, springs 61 for connecting the operating lever 55 to the knee of the toggle links, and the operating handle 59. The U-shaped frame 41 is fastened to the insulating base I of the circuit breaker proper by means of two screws 60. A pin 6| extends through aligned openings in the U-shaped base and engages the central frame member 2| of the moving contact assembly. This pin 6| provides a pivot point for both of the switch members 8 which are mechanically tied together by the insulating bar 3|.

Other holes are provided in the frame 41 for the reception of the pivot pins Bil-one on either side of the U-which provide pivot points for the bifurcated operating lever 55. The lower end of the toggle link 5| is pivoted to the end of the central frame 2| by the pin 65. The upper end of the link 5| is pivoted to the lower end of the toggle link 49 by means of the knee pin 65; and the upper end of the link 49 is pivoted to the trigger 69 by the pin 13. The pin 65 extends for some distance on either side of the links 5| and 49, and has means associated therewith for engaging the operating springs 61, one on either side (Fig. 6). The trigger 68, which is pivoted about the pin provides a releasably restraining means for holding the toggle links 48 and 5| in the operative positions.

The movement of the trigger 69 in a clockwise direction is limited by the projection 15,-which extends inwardly from one side of the U-shaped base 4.1. The movement of the bifurcated operating member is limited by the projections 11 and 19 which extend outwardly from the sides of the U-shaped base. A projecting member 8| is fastened to the operating handle 59 and provides a means for resetting the trigger 69. Y The projecting end 83 of the trigger 69 is releasably restrained by the latch means associated with the trip device 9.

Referring particularly to Figs. 5 and 6, it will be noted that the toggle links 49 and 5| are of parallel construction. This results in a more rigid structure and contributes to the ease of assembly. The parallel links 5| are fastened together by a. pin 84. This pin 84 engages a projection 85 on the trigger 69, and acts as a stop for limiting the movement of the knee of the toggle during the closing operation.

Aspreviously pointed out, the trip device 9 is entirely assembled upon the insulating base I. It comprises a latch 81, a latch retaining means 89, and two thermally responsive elements 9| for engaging and releasing the latch retaining means 89. Each of the thermally responsive elements 9I, as shown in this particular modification (Figs. 4, '1, and 8) is composed of bimetallic material. Each comprises a pair of leg portions 93 joined to each other-by a connecting" portion 95 so as to form a substantially U-shaped conducting loop, and a portion 91 which extends outwardly from the loop. Substantially L-shaped terminals 99 are fastened to the opposite ends of the U by means of the rivets 98 and connect, by means of the screws IIII and I93, to the conducting strips I95 and I01. Each of the conductin The latch 81 is essentially a centrally pivoted bell-crank lever. The projections I2I which extend downwardly toward the base I engage the pivot pin I23, and provide the pivot point. An opening I is provided in the end I24 of the lever for engaging the end 83 of trigger 69. The other end I21of the latch 81 is engaged by the latch retaining means 89. A spring I29 biases the latch in a counter-clockwise direction (Fig. 3) to the uniatched position.

The latch retaining means 89 includes a bodymember I3I, which extends across both poles and has two projections I32 for engaging pivot pins I38. An L-shaped iron member I33, two mica plates I35 and I31, and a flat iron member I39 are riveted to the body portion I3I by means of the rivets I4I; these provide a means insulated from the body member I3I for releasably engaging the projection I21 on the latch 81. In addition, they provide a means for engaging a spring. I43 which biases the latch retaining means to the retained position. Two overhanging projections I45 extend outwardly from the body portion I3,I. Each of these projections I45 has a threaded opening for engaging the stud I49 of an insulating knob I41. A nut I5I is provided for locking the stud I49 in position. The insulating knob I41 and the overhanging projection I45, together, provide means whereby a movement of the thermally responsive element 9| may be transmitted to the latch retaining means 89, to open the breaker. It should be noticed that since the projection I21 forms a stop limiting the clockwise rotation of the-latch retaining member 89 under the influence of its biasing spring I43, the thermally responsive element 9I is under no external stress of any sort when in its normal position so that there is notendency for'it to take a permanent set in a distorted position.

The latch 81 is supported in a U-shaped iron- -responsive elements.

, for mounting the breaker. I

Figs. 9 to 18, inclusive, illustrate various designs and modifications of the thermally responsive elements used in carrying out my invention. The reason for the various shapes employed and the advantages resulting from the use of each design 1n will be more apparent after an examination of the general characteristics of bimetallic thermally It is well known in the art that the deflection-of a bimetallic member, due

to heating, is proportional to the square of the 15 free length of that member. Thus, in the design of bimetallic thermally responsive elements; it is desirable to secure the maximum possible effective length, the minimum electrical resistance--if the element is directly heated by current flow 20 therethrodgh-and the most eflicient distribution of the surface and massto reduce the quantity of bimetal required. The various designs, and the modifications thereof, which I disclose in the application all fulfill as many of the above require- 25 ments as is possible for the particular current" condition and the particular time delay characteristic involved.

All'of the thermally responsive elements herein disclosed are primarily intended to be directly heatedthat is, terminals are provided, and it is intended that the currentv in the controlled circuit should fiow through a portion of the element, which portion serves as a heater. It is quite posslbfe, however, to utilize any or all of these designswith indirect or auxiliary heaters, and it is my wish and intention that the appended claims should cover structures of that type. Figs. 7 and 8, are enlarged views of the.bimetallic thermally responsive .element 9| used in the complete embodiment of my invention. This bimetal design is particularly adapted for moderatevalues of current. The current conducting loop or heater portion, formed by the two leg portions 93 and the conducting portion 95', is of appreciable area and permits the passage of considerable current without undue heating. Furthermore it is notiadily burned out by heavy short circuit currents. The projecting portion 91 is'likewise of considerable thermal capacity. Thus, the element BI is capable of carrying moderate currents continually without undue heating and with a low 1 R loss, and the mass distribution of the element is such as to introduce an appreciable time lag between the beginning of an overload condition and the deflection of the projecting portion 91 to a position where it opens the breaker. By making the conducting heater loop form only a part of the element proper, I am able to reduce'the amount of bimetallic material required while retaining the desired time interval, and in addition I am able to reduce the resistance of the heater. It is especially desirable to reduce the mass of the bimetal to a min mum because of the high cost of bimetallic thermally responsive material. The iron mem- 6-"). here H1, which are insulated from the end 91 of the bimetallic element 9| by the mica plates H9 and are fastened together by the rivets II5 serve to stiffen the free end of the element and make for more reliable operation. 7

The design I58 shown in Figs. 9'and 10 comprises a heater portion I54 and a projecting portion I56, the projecting portion being riveted to theLheater portion by means of two rivets I51.

Essentially, the heater portion is of substantially the same outline as the corresponding heater portion in the element 9I. It has two leg portions I59 and a portion I6I connecting the leg portions. The terminals I63, however, are formed integral with the heater portion. This design has several advantages for certain applications. It is particularly satisfactory for use in trip devices where large currents are to be carried with a minimum of deflection. Also it has considerable merit for applications where a considerable time delay is desired. The projecting portion I56 is of bimetallic material, and the heater portion I54 may or may not be of bimetallic material as is pointed out in some detail in the following paragraph.

If it is desirable to carry heavy currents, and if the trip device controlled by the thermally responsive element is actuable by a moderate deflection thereof, I prefer to use a material such as stainless steel for the heater portion I54. This material is considerably cheaper than bimetal, and, despite the cost of the riveting process, results in a cheaper thermally responsive element for higher currents. If, however, the currents to be carried are of comparatively small magnitude, and if it is desired to secure a maximum deflection, the heater portion I54 and the projecting portion I56 may both be formed of bimetallic material (Fig. 19). In this case, I prefer to use materials of different thicknesses for the two'portions. That is, .the heater portion is usually of heavier gauge plate than the projecting portion. This type of construction gives a somewhat greater deflection for the same heating effect than does the element in which the heater and projecting portions are of diiferent materials.

The design I19 shown in Figs. 11 and 12 is similar to the design shown in Figs. '1 and 8, except that the end portion has been simplified. It comprises a heater portion I65 having two leg portions I61, a connecting portion I69, and a projecting portion III, all formed integral with each other. The terminals I13 are riveted to the leg portions I61 by the rivets I15. The same advantages which are claimed for the bimetallic element 9I may he claimed for this elementthe conducting loop comprises only a part of the total length of the element, thus large deflection is secured with a small expenditure of energy, and a minimum mass of bimetal, consistent with the currents to be carried, is made possible. In addition, the design I10 has a simplified projecting portion I-1I, which aids considerably in reducing the cost of manufacture, the projecting portion I1I not being subject to buckling.

The design of bimetal I11, shown in Figs. 13 and 14, is a modification of thedesign I19, and is particularly adapted for handling very heavy currents. The usual terminals I81 fastened by the rivets I86, a conducting portion It", and a projecting portion I83 are provided. A portion I89 has been cut out between the terminals I81; this cut out portion defines two leg portions I19 and a second conducting portion. I85 which is shunted across the terminals I81. The size of the opening I89 depends upon the specific rating of the element under consideration, and its function is to alter the electrical circuit between the terminals and to divide the current path into two parts. The bimetal design I11 has low resistance between the terminals I81, and is of a design particularly adapted for stock "purposes. That is, blankforms having the general outline of the element I11 and having the terminals I81 may be placed in stock. Then, when it is necessary to construct a trip unit for a particular rating, the opening I89 may be punched out to suit that particular requirement. This design thereby cuts down in the number of stock forms which it is necessary to keep on hand, and provides a very satisfactory and a very economical method for securing thermally responsive devices of different current ratings.

The design I9l, which is shown in Figs. 15 and 16, is very similar to the design I10 with one exception-the two terminals I93 are formed by bending over the ends of the leg portions I92. This design reduces the points where the electrical circuit is maintained by pressure contact, and is effective in cutting down the heat losses.

The design I95, which is shown in Figs. 1'7 and 18, is of somewhat different form than the previously described designs, it being substantially H-shaped. The heater portion I91 comprises two leg portions I99 and a conducting portion 2M extending therebetween. In addition, two projecting members 293 extend outwardly from the heater portion. These members 203 are fastened to each other by means of two iron members 295, each insulated from the thermal element I95 by a mica strip 201, and rigidly fastened together by the rivets 209 which extend through suitable openings in the projections! and from which openings the rivets are insulated. The terminals 2 are fastened to the leg portions I99 by means of rivets 2I3. This design is of particular value when a considerable mass of bimetal is desired for securing a considerable time delay in the operation of the device, and when it is desirable, at the same time, to reduce the resistance of heater portion to minimum. The two projecting portions 293 provide the additional mass required, and the connection portion 2! reduces the resistance of the heater. The deflection of an H-shaped bimetal is substantially equal to'the deflection secured by a U-shaped bimetal having the same overall di mensions, and a considerable operating saving is efiected by the reduction of heat losses made possible with the H-shape. The amount of bimetal used is about the same for the H or the U shape.

The terminals on all of the bimetal elements shown in Figs. 7 to 18, inclusive, are positioned similarly, and any of the elements shown in Figs. 9 to 18 may be substituted for the element 9| illustrated in the other figures of the drawings,,

the screws IIII and I93 serving as fastening means.

In Figs. 1 to 6, the circuit breaker used in illustrating this embodiment of my invention is shown in the closed position. It will be noted that the knee pivot pin 65 of the toggle links 49 and 5| has moved to a point above (Fig. 3) the center line of the toggle. Thus the switch members 8 are locked in the closed position and maintain, through the agency of the flat springs 25, a substantially constant contact pressure. To open the breaker manually, the operating handle 59 is pushed in a counter-clockwise direction (Fig. 3) about its pivot point 63. This moves the springs 61 in a similar direction about the knee pivot 65, and at some point, before the limit of motion of the operating handle 59 has been reached, a component of force will be exerted by the springs 61, tending to move the knee pivot 65 to break the toggle downwardly toward the trip device 9.

A continued movement of the operating handle 59 will then cause the collapse of the toggle and the movement of the switch members I to 2 the open position, the switch members 8 being the opening operation. The operating handle isnow moved in a clockwise direction aboutthe pin 63, and as the movement progresses the spring.

' 81 exerts a force tending'to move the knee pivot 65 of the toggle upward, this movement being completely effected when the handle has nearly reached the closed position. The movement of the toggle links 49 and 5| during the closing process is restricted by the engagement of the pin 84 and the projecting portion 85 on the triggel 68.

In the event in either one of the circuits controlled by the switch members 8, the bimetallic thermally responsive element 9| in that particular pole will begin to deflect downwardly (Fig. 3). If the overload continues for a predetermined time interval, the free end 81 of the bimetal element 9| will eventually engage the insulating knob l and will move the latch retaining means 89 against its biasing spring I43 to the unlatched position. The projection l2! on the latch 8'! will then disengage the latch retaining means 89, and the latch 81 will rotate-in a counter-clockwise direction under the influence of its biasing spring I 29 and the bias of the spring 61 transmitted through the projection 83 of the trigger '88" This'movement of the latch 81-will release the'trigger 89 and permit it to rotate about its pivot ll until it engages the projection 15. This rotation otthe trigger 88 moves the pivot point 13 of the upper link '49 of the toggle mechanism to a point above the center line of the toggle (Fig. 3), and at the same time the projection 85 presses against the pin 84' thereby setting the knee of the toggle in motion. The toggle then breaks to the left (Fig. 5) under the influence of the springs G'Land in so doing opens the circuit controlled' by both the switch members. The time interval elapsing between the occurrenceof an overload condition and the opening of the breaker is dependent upon the magnitude of the overload; the interval being substantially inversely proportional to the magnitude of the overload.

After the breaker has been opened by the'trip device, it is necessary to restore the mechanism to an operative condition. In order to do this,

, the operating handle 59 ismoved counter-clockwise'about its pivot 83, (Fig. 3). The projection 8| of' the operating handle 59 engages the end.

6801 the trigger 89, and ,upon continued movement the operating handle 58 forcesthe trigger 68 to rotate in a counter-clockwise direction.

against the bias of the springs 61. As this movement continues, the end 8801 the trigger 69 enmanually, the thermally responsive element 9!- will be heated immediately and will release the latch retaining means in exactly the same man-' ner as before. The trigger 88 will thus here.-

of an overload or a short circuitleased, and the breaker will open regardless of the position in which the operating handle may be held.

It will thus be seen that ,I have Provided an. improved trip mechanism for multi-pole circuit breakers which is capable of opening all of the poles of the breaker after a very short time delay upon the occurrence of a short circuit, and after a predetermined longer time interval upon the occurrence of an overload condition, which is capable. of tripping a breaker irrespective of theposition of the operating handle, and which is resettable to the operative position by means associated with the operating handle. In addition,

I have disclosed designs for bimetallic thermally responsive elements which are simpler and more eflicient than previous designs of this type, and which may be manufactured at a lower cost.

Moreover, I have disclosed a trip device havmanent distortion of the bimetal will develop thus changing the amount of movement necessary to trip the breaker. This disturbs the operation of the thermally responsive devices and alters the .the breaker operating means considerable per- 25 calibration of the thermal element-both of which 30 are very undesirable results ,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 will be desirable in many applications. I desire, therefore, that the language of the accompanying claims shall 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. In electrical apparatus, a thermally responsive device including asubstantially U- shaped heater of conducting material, and a separate member of bimetallic 'material thermally conductively joined to said heater and extending outwardly therefrom.

2. In electrical apparatus, 'a member of bimetallic material having a pair of electrical terminals, and a current carrying heater portion between .said terminals, said current carrying portion having a hole therein for defining two parallel current carrying paths, one on either side of saidhole, said hole being spaced from the edges of saidcurrent-ca'rrying member.

3. In electrical. apparatusra. thermally reconductively-joined to said heater adjacent the closed end of said U and which extends outwardly therefrom. I 4. In electrical apparatus, a thermally .re-

sponsiv'e device comprising a substantiallyH shaped member entirely of bimetalliomaterial' and means got insulating material extending across the side-portions oi the H at at least one end thereof."

sponsive device having a pair of elctrical terminals, a looped current carrying heater oi non bimetallic material extending between said term'i-.

5. In electrical pp rat s. a thermally re- 3 nals, and a separate member of bimetallic material projecting outwardly from the closed end of said looped heater, said-projecting portion being thermally conductively joined to said heater portion.

6. In a circuit interrupter, a switch member for opening the circuit, means for biasing said switch member to the open position, releasable means for holding said switch member in the closed position against said biasing means, and a. releasable retaining means operable by a thermally responsive element, said retaining means and said thermally responsive element movingv substantially in the same direction to trip said interrupter, said retaining means having an overhanging projection thereon for engaging said thermally responsive element, said thermally responsive element being normally out of contact with said retaining means.

7. In a circuit interrupter, a switch member for opening the circuit, means for biasing said switch member to the open position, a releasable latching means for holding said switch member in the closed position against said biasing means,

a thermally responsive element, and a pivoted,

releasable latch retaining means operable by said thermally responsive element, said thermally responsive element being fixed at one end and hav- I ing a portion extending along said latch retaining means, said latch retaining means being pivoted at a point adjacent to said fixed end of said thermally responsive element, and having means associated therewith for engaging said thermally responsive element, said thermally responsive element and said latch retaining means moving in substantially the same direction whenreleasing said latch.

8. In a circuit interrupter, a switch member for opening the circuit, spring means for biasing said switch member to the open position, .a releasable latch and a contact restraining member for releasably restraining said switch member in the closed position against the bias of said spring means, a latch retaining means for engaging and operating said releasable latch, and a member of bimetallic material for engag n and releasing said latch retaining means, said releasable latch comprising a centrally pivoted member engaged at one end by said contact restraining member and prevented from turning under the transmitted force of said spring means by said latch retaining means, said latch retaining means being pivoted at one end and having a portion for engaging said bimetallic member which is fastened at one end adjacent to the pivot point of said latch retaining means and is free to move at the other end.

9. In electrical apparatus a thermally responsive device comprising a substantially H- shaped member of bimetallic material having terminals at one end thereof, and having means for joining the side portions at the other end thereof in order to prevent buckling of said device during its operation.

10. In electrical apparatus, a thermally responsive device including a looped heater of himetallic material, and a member of bimetallic material extending outwardly from said looped heater, said heater and said outwardly extending member being formed from sheet material of difiering thicknesses.

11. In electrical apparatus, a thermally responsive device includinga substantially U- shaped heater of bimetallic material, and a member of bimetallic material thermally conducaosaass tively joined to said heater adjacent the closed end of said U and extending outwardly therefrom, said heater and said outwardlyextending member being formed from sheet material of differing thicknesses.

12. In electrical apparatus, a thermally responsive device comprising a current-carrying heater which includes means for defining a pair of leg portions and means for electrically connecting said leg portions, and a separate member of bimetallic material thermally conductively joined to said heater and extending outwardly therefrom.

13. In electrical apparatus, a thermally responsive device comprising a substantially U- shaped, current-carrying means of bimetallic material, and a separate means mechanically joined to said current-carrying means and extending outwardly therefrom for a considerable distance along the plane of the means of bimetallic material, said separate means being adapted to engage and actuate said apparatus.

14. In a circuit interrupter, a switch member for opening the circuit, means movable to cause said switch member to move to the open position, means for biasing said movable means to cause said switch member to move to the open circuit position, releasable latching means for restraining said biasi'ng means from moving said movable means to cause the opening of the circuit through said interrupter, and a thermally responsive element for causing said latch means to release said biasing means upon the occurrence of.

predetermined conditions, said thermally responsive element being'flxed at one end and having a movable portion, said latchingmeans including responsive element and said latch member mov-- ing in substantially the same direction to release said biasing means.

15. In a multi-pole circuit'interrupter, contact means including movable switch members for each of a plurality of poles, means movable to cause at least one of said switch members to move to the open circuit position, means for biasing said movable means to a. position where at least one of said switch members is caused to move to the open circuit position, releasable latching means for restraining said biasing means .irom causing the opening of said circuit interrupter, and a plurality of thermally responsive elements, each heated in response to the current flowing through one of the poles of said interrupter, for causing said latch means to release said biasing means upon the occurrence of predetermined conditions in any one of the poles of said interrupter, each of said thermally responsive elements comprising a member fixed at one end and having a movable portion, said latching means including a single latch member that is supported through the agency of pivot means whose axis extends adjacent the fixed end of each of said thermally responsive elements, said latch member having a portion extending along the movable'portion of each of said thermally responsive elements and being actuable to release said biasing means by movement of any one of said thermally responsive elements, the movable portion of each of said thermally responsive elements and of said latch member moving in Substantially th 75 same direction when effecting the release of said .metallic element, which member is movable independently of said latch in response to movement of said bimetallic element to effect the release of said latch, said bimetallic element having a fixed end and a movable end normally free from external stress. 17. In a circuit. interrupter, separable contac means, actuating means for causing said contact means to be moved to the open and to the closed circuit position with a snap action, means associated with said actuating means for biasing said contact means to the open circuit position when said interrupter is-in the closed circuit position, and a trip means which normally prevents said biasing means from causing said contact means to move to the open circuit position, but which is operable upon the occurrence of predetermined conditions to cause said biasing means to separate said contact means at high speed, said'trip means including a latch, biased to the unlatched position, for engaging said biased actuating sponsive element moving to engage and operate.

'said actuating means forbiasing said contact means, a latch retaining member biased to the retained position, and a current carrying, thermally responsive member normally out of contact with said latch retaining means,-said thermally resaid latch retaining member upon the occurrence of predetermined conditions.

18. In a circuit interrupter, separable contactmeans, actuating means, including an operating member, for causing said contact means to be moved to the open and to the closed circuit position with a snap action, and a trip means operable upon the occurrence of predetermined con ditions to cause said actuating means to automatically move said contact means to the open circuit position with" a snap action, regardless of the position of said operating member, said trip means including a latch, a bimetallic, thermally responsive element, and a member intermediate said latch and said bimetallic element, which member is movable independently of said latch in response to movement of said bimetallic element to effect the release of said latch, said bimetallic element having aflxed end and a movable end normally free from external stress. 7

1 19. In a circuit interrupter, separable contact means, actuating mear l,- including an Joperating member, ior causing said contact means to be moved to the open' and to the closed circuit position with a snap action, means associated with means to the open. circuit position when said interrupter is in the closed circuit position, and a conditions to cause said biasing means to separate said contact means at high speed, regardless of the position of said operating member, said trip means which normally prevents said bias-,

ing means from' causing said contact means to move to the open circuit position, but which is.

operable upon', the occurrence .of predetermined trip means including a latch for normally restraining said biasing means; a bimetallic,'thermally responsive element, and a member intermediate said latch andsaid bimetallic element, which member is movable independently of said latch in response to movement of said element to efiect the actuation of said latch, thereby allow-- ing said biasing means to move said contact means to the open circuit position, said bimetallic element having a fixed end and a movable end normally free from external stress.

20. In a circuit interrupter, a switch member for opening the circuit, means movable to cause said switch member to move to the open position, means for biasing said movable means to cause 15 said switch member to move to the open circuit position, releasable latching means for restraining said biasing means from moving said movable meansto cause the opening of the circuit through said interrupter, and a thermally responsive element for causing said latch means to release said biasing means upon the occurrence of predetermined conditions, said thermally responsive element havinga fixed end and a movable end normally free from external stress, said latching means including a member that is pivotally supported adjacent the fixed end of said thermally responsive element and that has a portion extending along said movable portion of said thermally responsive-element, the movableportion ofsaid thermally responsive element and said latch member moving in substantially the same direction to release said biasing means.

21. In a circuit interrupter, a switch member for opening the circuit, means movable to cause said switch member to move to the open position, means for biasing said movable means to cause said switch member to move to the open I circuit position, releasable latching means for restrainingsaid biasing means from moving said movable means to cause the opening of the circuit through said interrupter, and a thermally respon- -sive element for causing said latch means to re-- lease said biasing means upon the occurrence ofpredetermined conditions, said thermally respon- 'siv e element having a fixed end and a movable end normally free from external stress, said latchin g means including a member that is pivotally supported at the end thereof which is nearest. said fixedend of said thermally responsive element and that has a portion extendingfalong said movable portion of'said thermally responsive ele-' ment, the movable portion of said thermally re-' sponsive elementand said latch member' mov- 'ing in 'substantially'the same direction to release. said biasing means.

22. In a multi-pole circuit interrupter; contact means for opening and for closing a plurality of poles; actuating means for said contact means,

including means movable to causesaid contact 0 meansto move to the open circuit position and means for biasing said movable means to-cause said contact means to move to the op'encircuit position; a releasable latching means for restraining said biasing means from moving said movable means to cause the opening of the aircuit through said interrupter; and a 'plurality.

of thermally responsive elements for causing said latch meansto release said biasingme'ans upon the occurrence of predetermined conditions, each 7 of said thermally responsive elements being fixedat one end and having a movablev portion; said latching means including a singlelatch member and a; latchretaining-member which has a'portion extending across two or more poles of said interrupter; said latch retaining member being pivotally supported at its end nearest the fixed ends of said plurality of thermally responsive elements, having a portion extending along the movable portion of two or more of said thermally responsive elements, and being movable to cause the release of said latch member by any one of two or more of said thermally responsive elements; the movable portion of each of said thermally responsive elements and said latch retaining member moving in substantially the same direction to release said biasing means.

23. In a circuit interrupter, separable contact means, actuating means for moving said contact means to the open and to the closed circuit position with a snap action, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit'position, likewise with a snap action, said trip means including a latch, a bimetallic thermally responsive element, at least one member intermediate said latch and said bimetallic element, which member is movable independently of said latch in response to movement of said bimetallic element to efiect the release of said latch, means biasing said movable member against movement to efiect the release of said latch, and a stop means for preventing said biasing means from moving said intermediate member beyond a predetermined point.

24. In a circuit interrupter, separable contact means, actuating means for moving said contact means to the open and to the closed circuit position with a snap action, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit position, likewise with a snap action, said trip means including a latch, a bimetallic, thermally responsive element, at least one pivotally supported member intermediate said latch and said bimetallic element, which member is movable about its pivot point in response to movement of said bimetallic element to eflect the release of said latch, spring means biasing said movable member against movement to eifect the release of said latch, and a stop means for preventing said spring biasing means from moving said intermediate member beyond a predetermined point.

25. In a circuit interrupter, a base member, separable contact means and actuating means for moving said contact means to the open and to the closed circuit position, supported on said base, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit position, said trip means being supported on said base and including a latch, a bimetallic, thermally responsive element, one end of which is fixedly supported adjacent said base and the other end of which is freely movabl at least one member intermediate said latch and said bimetallic element, which intermediate member is movable independently of said latch in response to movement of said movable and of said bimetallic element to effect the release of said latch, said intermediate member having at least a portion thereof which extends along said bimetallic element and being adapted to move in the same direction as said movable end of said bimetallic element when eifecting the release of said latch, means biasing said intermediate member against movement to effect the release of said latch, and a stop means for preventing said biasing means from moving said intermediate member beyond a predetermined point.

26. In a circuit interrupter, a base member, separable contact means and actuating means for moving said contact means to the open and to the closed circuit position, supported on said base, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit position, said trip means being supported on said base and including a latch, a bimetallic, thermally responsive element, one end of which is fixedly supported adjacent said base and the other end of which is freely movable, at least one member intermediate said latch and said bimetallic element, which intermediate member is pivotally supported at the end thereof which is nearest said base and is movable in response to movement of said bimetallic element to effect the release of said latch, said freely movable end of said bimetallic element and said intermediate member moving in the same direction when efopen and to the closed circuit position with a 3 snap action, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit position regardless of the position of said operating member, said trip means including a latch, a bimetallic, thermally responsive element, at least one member intermediate said latch and said bimetallic element, which member is mov-- able independently of said latch in response to movement of said bimetallic element to effect the release of said latch, said bimetallic element having a fixed end and a movable end which is normally, substantially free from external stress. means biasing said intermediate member against movement to effect the release of said latch, and a stop means for preventingsaid biasing means from moving said intermediate member beyond a predetermined point.

28. In a circuit interrupter, separable contact means, actuating means for moving said contacts to the open and to the closed circuit position with a snap action, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit position, likewise with a snap action, said trip means including a member movable to effect the operation thereof, a bimetallic, thermally responsive element, at least one member intermediate said movable member and said bimetallic element, said member which is movable to effeet the operation of said device engaging said intermediate member with a latching engagement, said intermediate member being movablein response to movement of said bimetallic element to disengage said movable member, means biasing said intermediate member against movement to disengage said movable member, and a trip device including a member movable to effect the operation thereof, means biasing said member to efiect theoperation of said trip device, a bimetallic, thermally responsive element, at least one member intermediate said movable member and said bimetallic element, said member which is movable to effect the actuation of said trip'device engaging said intermediate member with a latching engagement, said intermediate member being movable in response to movement of said bimetallic element to disengage said movable member and thereby effect the operation of said trip device, and stop means for preventing said intermediate member from being moved beyond a predetermined point by the reaction forces of said biasing means for said member which is movable to actuate said device when that member and said intermediate member are in latching engagement with each other.

-30. In a circuit interrupter, separable contact means, actuating means for moving said contact means to the open and to the closed circuit position and a trip device operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit position, said trip device including a pivotally supported member movable to effect the operation of said trip device, means biasing said member to effect the operation of said trip device, a bimetallic, thermally responsive element fixedly supported at one of its ends, the other end of said element being movable, at least one member intermediate said member movable to actuate said trip device and said bimetallic element,. said member movable to efifect the actuation of said trip device having a latching portion for engaging cooperating latching means forming a part of said inter,

mediate member, said intermediate member bemg pivotally supported adjacent the fixed end of said bimetallic element and having a portion extending along the movable portion of that element, and said intermediate member being mov-- able by said bimetallic element to effect the release of said latching portion in order to allow said movable member to move so as to eflect the actuation of said trip device, and stop means for preventing the reaction forces of said biasing means which are transmitted from said member movable to actuate said trip device to'said intermediate member when those members are in latching engagement with each other from moving said intermediate member beyond a predetermined point.

31. In a circuit interrupter, separable contact means, actuating means for causing said contact means to be moved to the open and to the closed circuit position, and a trip device operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit position, said trip device including a member movable. to effect the operation thereof.

means biasing said member to effect the operation of said trip device, a bimetallic, thermally responsive element, at least one member intermediate said movable member and said bimetallic element, said member which is movable to effect the actuation of said trip device engaging said intermediate member with a latching en-- gagernent,.said intermediate member being movable in response to movement of said bimetallic' element to disengage said movable member and thereby effect the operation of said trip device,

means biasing said intermediate member against movement to disengage said member which is movable to eifect the operation'of said trip device, and stop means for preventing said intermediate member from' being moved beyond a predetermined point by the force of the biasing means for said intermediate member, or by the reaction forces of said biasing means for said member which is movable to actuate said trip device, these reaction forces being transmitted to said intermediate member through said latching engagement.

32. In a circuit interrupter, separable contact means, actuating means for moving said contact means to the open and to the closed circuit position, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating meansto automatically move said con-- tact means to the open circuit position, said trip means including a latch, a bimetallic thermally.

responsive element, a pivoted member interme-:

diate said latch and said bimetallic element:-

which member is movable independently of said latch inresponse to movement of said bimetallic element to effect the release of said latch, said' bimetallic element having a fixed end and a mov-l able end normally free from external stress.

33. In a circuit interrupter, separable contact means, actuating means for moving said contact means to the open and to the closed circuit position, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating means to automatically move said contact means to the open circuit position, said trip means including a pivotally supported latch, a bimetallic thermally responsive element, a pivotally supported latch retaining member biased to the retained position and movable, independently of said latch, in response to movementof said bimetallic element to release said latch, said bimetallic element having a fixed end and a movable end normally free from external stress.

34. In a circuit interrupter, separable contact means, actuating means for moving said contact means to the open and to the closed circuit position, and a trip means operable upon the occurrence of predetermined conditions to cause said actuating meansto automatically movesaid contact means to the open circuit position, said trip means including a latch, a bimetallic thermally responsive element, at least one pivotally supported member intermediate said latch and.

said bimetallic element, which member is movable about its pivot point in response to movement of said bimetallic element to effect the relel short legs of uniform narrow section and relatively high resistance and quickly deflectible as the result of excess current therethrough and comprising adjacent its outer end a long unslotted body portion deflectible only to a negligible extent as the result of the said current but never- 'theless subject to delayed deflecting by reason oi heat transmitted from the current heated legs, the said long body portion of the strip having therein between the ends thereof a portion sharply reduced in area to restrict the heating of the said body portion.

36. In a current responsive device, a strip of bimetallic material, a slot in one end of said strip, means for making a pair of current connections to said strip, one of said connections being at each side of said slot whereby the current flows in a looped path about said slot and causes said end of the strip to be quickly heated and deflected upon the flow of excess current, the other end of said strip extending a distance beyond the end of said slot at least as great as the length of said slot, and said strip having a portion sharply reduced in width between the end of said slot and the other end of the strip for restricting the flow of heat from said looped path to the other end of the strip.

actuation of the device, and said long portion being greatly reduced in width a short distance beyond the inner end of said cut out portion.

aosaaee 38. For use as the current-responsive element of an automatic circuit'breaker, a U-shaped bimetallic current-carrying strip slotted adjacent its inner or supporting end to provide two legs of relatively high resistance and quickly deflectible as the result of excess current there:- through and comprising adjacent its outer end a long unslotted body portion deflectible only to a negligible extent as the result of the said current but nevertheless subject to dela; ed deflecting by reason of heat transmitted from the current heated legs, the said long body portion of the strip extending beyond the end of the slot a distance at least as great as the length of the slot and said long body portion having therein between the ends thereof a portion sharply reduced in area to restrict the heating of the said body portion.

39. In a circuit interrupter, a switch member for opening the circuit, means for biasing said 20 to said latch controlling member, said latch con- 30 trolling member being pivoted at its end nearest to said fixed end of said thermally responsive element, and having means associated therewith to be engaged by said thermally responsive element, said thermally responsive element and said 35 latch controlling member moving in substantially the same direction when releasing said latching means.

D. DGR.