US2656440A

US2656440A - Circuit breaker

Info

Publication number: US2656440A
Application number: US270403A
Authority: US
Inventors: Hiller D Dorfman
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1952-02-07
Filing date: 1952-02-07
Publication date: 1953-10-20
Anticipated expiration: 1970-10-20

Description

Oct. 20, 1953 2,656,440

H. D. DORFMAN CIRCUIT BREAKER Filed Feb. '7, 1952 Hiver D.Dorfman ATTO R N Patented Oct. 20, 1953 CIRCUIT BREAKER Hiller D. Dorfman, Beaver, Pa., assigner to Westinghouse Electric Corporation, East Pittsburgh. Pa., a corporation of Pennsylvania Application February 7, 1952, Serial N0. 270,403

14 Claims.

This invention relates to circuit breakers and more particularly to circuit breakers for controlling lighting and moderate power circuits.

An object of the invention is to provide a circuit breaker having a thermally responsive trip device with means for compensating the trip device for changes in ambient temperature and means for limiting the amount of compensation.

Another object of the invention is to provide a circuit breaker embodying thermally responsive trip means with means for compensating the trip device for changes in ambient temperature and means for limiting the amount of compensation wherein the compensating means is mounted separate from the thermally responsive trip means.

Another object of the invention is to provide a circuit breaker embodying thermally responsive trip means and a trip member operable by the trip means to effect opening of the breaker with means mounted on said trip member for compensating said thermally responsive trip means for changes in ambient temperatures and means also mounted on said trip member for limiting the amount of compensation.

Another object of the invention is to provide a circuit breaker embodying thermally responsive trip means and a trip member with compensating means mounted on the trip member and engageable by the thermally responsive means to eiiect operation of the breaker, said compensating means compensating said thermally responsive means for changes in ambient temperatures and means also mounted on the trip member for limiting the amount of compensation provided by the compensating means.

Another object of the invention is to provide a circuit breaker according to the preceding paragraphs characterized by the provision of means for calibrating the compensation limiting means.

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

In said drawing:

Figure 1 is a side elevational view, partly in section, of a circuit breaker embodying the principles of the invention,

Fig. 2 is a view similar to Fig. 1 showing a modication of the trip device applied to a somewhat difierent type` of circuit breaker,

Fig. 3 is a sectional view taken on line III-III of Fig. 1 of the trip member associated with the circuit breaker illustrated in Fig. 1,

Fig. 4 is a sectional view taken on line IV-IV of Fig. 2 of the trip member associated with the circuit breaker illustrated in Fig. 2.

Referring to Fig. 1 of the drawing, the circuit breaker is of the three-pole type and is mounted in a housing comprising a base and a removable cover |3, both of molded insulating material. Each pole of the breaker (only the center pole being shown) includes a stationary contact I9, an are extinguisher 2|, and a movable contact 23. The stationary contact |9 is mounted on the inner end of a strip 25 of conducting material, the other end of which is secured to a terminal 21.

The movable contact 23 is carried on the free end of a spring contact arm 29 which is secured to a U-shaped switch member 3|. lThe movable contact 23 is electrically connected by means of a flexible conductor 33, to the current responsive trip means of the trip device which will be hereinafter described. The current responsive trip means is, in turn, connected to a conducting strip 35 having a terminal 31 secured to the outer end thereof. The contacts, switch members and trip means for the three poles of this breaker are of substantially identical construction; hence only one pole has been shown and described.

The three movable switch members 3| are mounted for simultaneous movement about a common axis by means of a sectional pivot shaft 39, the center section of which is supported in the side Walls of a U-shaped frame 4| secured to the base of the breaker. The switch members 3| of the outer poles (not shown) are secured to the outer sections of the pivot shaft 39, and are mechanically connected to the center pole switch members, but insulated therefrom, by insulating connecting hubs 43 (only one being shown) which connect the three separate sections of the pivot shaft together. A stop pin 45 extending through the frame 4| cooperates with projections formed on the center pole switch member 3| to limit the opening movement of the assemblage of switch members.

A single operating mechanism is provided for simultaneously actuating the switch members of all three poles of the breaker to open and closed positions. The operating mechanism is mounted in the frame 4|, and comprises a U-shaped operating member 4l having its legs pivoted on pivot members 49 struck out from the frame 4|, a releasable carrier lever 5| pivoted on a pivot pin 53 in the frame 4|, a pair of toggle links 55 and 51, and overcenter springs 59 (only one being shown). The toggle links 55 and 51 are pivotally connected together by means of a knee pivot pin 6|. The inner toggle link 55 is pivotally connected by a pivot pin 63 to the center pole switch member 3|. The toggle link 51 is pivotally connected at its outer end by a pivot pin B to the releasable carrier lever 5|. The overcenter springs 59 have their outer ends connected to the bight portion of the U-shaped of the handle. Lugs 12 are struck out from the sides of the frame 4| to limit the opening and closing movements of the operating member 41.

The breaker contacts are manually opened by clockwise movement of the operating handle from the position in which it is shown in Fig. 1. This movement carries the line of action of the overcenter springs 59 across to the right of the pivot pin 65 whereupon the force of the springs causes collapse of the toggle 55-51 thereby moving the movable contacts to the open position with a snap action. The contacts are closed by counterclockwise movement of' the handle back to the Fig. 1 position. This moves the line of action of the springs 59 across to the left of the pivot pin 65, at which time the springs actuate the toggle 55-51 to its extended overset position shown, thereby moving the movable contacts to the closed position with a snap action.

The trip device of the circuit breaker includes a latch 13 pivotally mounted on a pivotl pin 15 supported in the frame 4|. An extension 19 of the latch is provided with an opening 8|, one edge of which engages the free end of the carrier lever 5| and releasably restrains the carrier in normal position. The latch 13 is also provided with an extension 83 having an opening 85 thereon. A trip bar 81 of molded insulating material, and common to all of the poles of the breaker, is mounted for rotation by means of a shaft 89 molded therein, the ends of which are mounted in brackets 9| (only one being shown) secured to the base of the housing. An arcuate latch member 93 is molded into the trip bar in alignment with the opening 85 in the latch member 13. In the latching position of the parts, the carrier 5| is latched by the main latch 13 which, in turn, is held in latching position by the latch member 93. A spring 95 coiled about the pivot pin 15 biases the latch member 13 in unlatching direction and also biases the trip bar 81 to latching position. The trip bar 81 is provided with a plurality of compensating bimetal elements S1, one for each pole of the breaker.

Each of the compensating bimetals 91 is secured to a projection 94 on the lower side of the trip bar by means of a screw 9 6 and extend upwardly around and across the trip bar 81 and is provided with an integral extension 98 Which forms a loop portion above the trip bar 81.

Each pole of the breaker is provided with an overload trip device including a tripping bimetal element |0| having a mounting foot formed at right angles thereto by which the bimetal element is secured to the base of the breaker', the mounting foot being secured by means of a screw |03 to a metal insert |05. At its free end, the bimetal element |0| carries an adjusting screw |01 having a rounded inner end for engaging the extension 98 of the compensating bimetal element 91 and operating the trip bar 81 upon de ection of the tripping bimetal element. The free end of the tripping bimetal element is connected to the conducting strip by a flexible conductor |09, and the flexible conductor 33 connects the foot of the tripping bimetal element to the movable contact 23 as shown in Fig. 1.

yBy securing the compensating bimetal element 91 to the trip bar 81 and spacing it a substantial distance from vthe current responsive bimetal element |0| which is heated by the current of y the circuit, the compensating bimetal element is unaffected by the heat of the current responsive bimetal element, thus providing more accurate compensation for changes in ambient temperatures.

The high-expansion side of the tripping bimetal element |0| is on the right-hand side thereof. Also, the high-expansion side of the compensating bimetal element 91 is on the righthand side and inside the loop as viewed in Fig. 1; consequently the bimetal elements bend in the same direction inY response to changes in the temperature of the surrounding medium, maintaining substantially the same distance of the rounded end of the screw |01 from the extension 88 of the compensating bimetal element 91 during changes in ambient temperature.

Means is provided for limiting the temperature compensation provided by the compensating bimetal element 91 to a predetermined portion of the range of ambient temperature. This means comprises a projection ||0 on the trip bar 81 extending into the loop of the compensating bimetal element. As the compensating bimetal element 91 deiiects toward the left (Fig. l) in response to a predetermined increase in ythe temperature of the surrounding medium the extension 98 on the compensating bimetal element engages or is arrested by the projection H0 thus preventing further deflection of the compensating bimetal element and compensation for further increase in ambient temperature.

By way of example, the compensating bimetal element 91 may be set to deect the distance from the position in which it is shown in Fig. 1 to the point where it engages the projection ||0 in response to an increase in ambient temperature from, for instance, 25 centigrade to 75 centigrade. Therefore, the bimetal element 91 will compensate the tripping bimetal element |0| for changes in ambient temperature below 75 centigrade. After the deflection of the compensating bimetal element 91 is stopped by its engagement with the projection ||0 there is no further deflection thereof and no further compensation. The tripping bimetal element |0| will, therefore, trip the breaker quicker in response to a given overload current at temperatures above 75 centigrade than it would if the limiting projection ||0 were not provided. Thus the compensating bimetal element 91 is free to compensate only for ambient temperature below the temperature at which its deflection is stopped. It will be obvious that the compensating bimetal element can be set so that its deiiection in response to increases in ambient temperature will be Stopped at any desired temperature.

When an overload current occurs, the tripping bimetal element vbecomes heated by the current flow and when heated a predetermined amount, bends toward the left and engages the extension 98 of the compensating bimetal element 91. Further bending of the bimetal element |0| acts through the compensating bimetal element to cause counterclockwise rotation of the trip bar 81 and effects release of the latch 13 whereupon the overcenter springs 59 rotate the carrier lever counterclockwise. During this movement the pivot 65 is carried across to the left of the line of action of the overcenter springs which causes collapse of the toggle 55--51 and opening movement of the switch member 3| and opening of the breaker contacts.

Before the contacts can be closed following an automatic opening operation, the carrier lever 5| must be reset to the latched position. This is effected by clockwise movement of the handle to a position slightly beyond the ofi position,

. During this movement, a projection 09 on the operating member 41 engages and moves the car rier lever 5| back to the latching position. The spring 95 then rotates the trip bar 01 to its latching position as shown in Fig. l. The circuit breaker may then be closed by movement of the handle to the on position in the previously described manner.

Fig. 2 illustrates a modification of the invenm tion applied to a somewhat different circuit breaker. The circuit breaker shown in Fig. 2 comprises a, base and a removable cover H3, both of molded insulating material. This breaker also is of the three-pole type (only the center pole being shown) and includes a stationary contact H9, an are extinguisher |2| and a movable contact |23. The stationary contact is mounted on the inner end of a strip |25 of conducting man terial, the other end of which is secured to a terminal |21. The movable contact |23 is carried on the free end of a switch arm |29 and is connected by means of a flexible conductor |33 to the current responsive trip means `which will be described hereinafter. The current responsive trip means is, in turn, connected to a conducting strip |35 having a terminal |31 secured to the outer end thereof. The contacts, switch members and trip means for the three poles of this breaker are of substantially lthe same construction; hence only one pole has been shown and described.

rThe three switch members |29 are mounted for simultaneous movement about a common axis by means of an insulating pivot shaft |39 pivotally mounted in the side Walls of a U-shaped frame |4| secured to the base of the breaker. The switch members |29 of the outer poles (not shown) are secured to the ends of the pivot shaft The operating mechanism, which is similar to the operating mechanism of the circuit breaker illustrated in Fig. l, is mounted in the U-shaped frame |l|| and comprises an operating member |41 having its legs pivoted on pivot pins |49 supported in the side members of the frame |41, a releasable carrier lever |5| pivoted on a pin |53 in the frame IM, a pair of toggle links |55 and |51 and an overcenter spring |59. The toggle |55-I 51 interconnects the center pole switch member |29 and the carrier lever |5| in the same manner as was described for the breaker shown in Fig. l, and the overcenter springs |59 are connected to the knee of the toggle and to the operating member |41. An operating handle |61`lis secured to the outer end of the operating member |41 and 4is providedwith a handle portion eiliending through an opening |69 in the cover The breaker contacts are manually opened by clockwise movement of the handle from the position shown in Fig. 2. This movement carries the line of action of the overcenter springs |59 across to the right of the toggle link |51 whereupon the overcenter springs cause collapse of the toggle thereby moving the switch members |29 to the open position to open the contacts. The contacts are closed by reverse movement of the handle back to the position shown in Fig. 2.

Each pole of the breaker is provided with an overload trip device including a tripping bimetal element 20| secured to a conducting member 205 which, in turn, is secured to the base of the breaker by the screw |63 by which the base |6| of the trip device is secured. At its free end the compensating bimetal element |91 carries an adjusting screw 201 having an insulating button 208 on the end thereof which is engaged by the tripping bimetal upon thermal bending thereof to actuate the trip bar |81. The free end of the tripping bimetal element 20| is connected to the conducting strip |35 by means of a flexible conductor 209 and the conducting member 205 and flexible conductor |33 connect the tripping bimetal element to the movable contact |23.

More accurate compensation of the tripping bimetal element 20| for changes lin ambient temperatures is provided by spacing the compensating bimetal element |91 an appreciable distance therefrom so that the compensating bimetal element is unaffected by the heat of the current respons-ive tripping bimetal element 20|. The insulating button 208 also prevents transfer of heat from the current responsive bimetal element 20| to the adjusting screw 201 and to the compensating bimetal element.

The high-expansion sides of the tripping bimetal element 20| and the compensating bimetal element |91, respectively, are on the left-hand sides thereof. Consequently, both of these elements bend in the same direction in response to changes in the temperature of the surrounding medium. This maintains a substantially constant distance between the adjusting screw 201 `7 Y the tripping bimetal 'element -2 0| as the amblnt temperature varies.

The ambient temperature compensation'pro- 4vi'led by the compensating llinetal element |91 (Fig. 2) 4is l'irn'itec'l by means lo'f a limit stop 'meinber -2H secured to tl'iejtrip bar |87 and extending upwardly to the 'righi-.rot the compensating bimetal "elee'meritv |91. The limit stop member 2| stops the deilection of the compensating bimetal element |97 in response to an increase in ambient temperature to, 'for instance, 75 centigrade. The compensating bimetal element |'9`'| will, therefore, 'compensate the tripping bimetal 'element for :increases ambient temperature up to centigradi?. For changes in ambient itempertii're 7above '157 "ntigr'ade, there is no Vfurther 'denectionbf the "compensating bimetal element l and, hence, no further compensation. Vlvfear'is 'is provided for Calibrating the l'upper :limit 'of al'nbier'it temperature compensation profvid'ed 'by the compensating bimetal element F941. This means comprisesan adjusting screw 2| 3 'uxir'eadediy mountedin the limit stop member 2| adjacent its upper end. By Vadjusting the screw '213, the deetion 'of lthe compensating bimetal element in response toa rise'in ambient temperature may be vvaried `,thus varying the maximum temperature at which compensation is provided. n Upon thejoccurrence of an overload current, 'the tripping bmetall'el'ment 20| is Vheated by the flow of current therethrough, and when heated a predeteininedamount bends 'toward lthe right to eri/gage theedjustin'gscrew 287 and actuate "the'tripba'i' |81. 'Actuation of the trip bar causes tiie'iatchineiiiber 193 'to release the leren n3,

whereuponthe'ovei'center springs |58 rotatethe ca'rrierlev'e'r |`5| counterolockwise This movemeritfof 'the carrier lever |5| carries the Atoggle lin'k 1|51 across the left or" "the line of vaction 'f ythe ovrc'eriter springs which immediately causescoiiapse of me 'toggle 155-151 and movement of the sivitch members |29 to the open position and'ope'ning of the breaker'contacts.

lBefore the 'contacts can be closed following 'anitmatio'tpp'ngoperation, 'the carrier lever m niiist'be reset 'to the iatc'rred position. This is fa'ccoiiip'lished by movement of the handle |61 'in Vac'loeliivis'e"direction as far as it'will go. Duringthis xn'ovenienta projection |99 on the op- 'erating member I'Al' engages and moves the car- 'rir'lever back tothe ltoliing position. During the 'latter 'part of the resetting movement, the free end f the carrier lever wipes by the latch V|"I'3 which is thenres'toredto 'its l'atehing position by the spring |95. The circuit breaker v'may then 'be V'closed by movement Vof the handle to Vthe "on" position in the previously described mannen The invention provides a circuit breaker A'embodying acurrentresponsvetrip deviceandlh'avling animproved'ambient temperature compensating means'thatis'mounted away from thetrfip `means. `:By'thisconstruction, the compensating :bimetal element V-is mounted an appreciable distance `from kthe Ytripping vbimetal element which is heated by the current'of the circuit. In Vthis man-ner, the compensating `bimetal elementlis unaffected-by the-heat of -the tripping `bimetal -elenient. The-invention providesvmeans forlimiting the amount vof compensation provided by the ambient temperature compensating means and alsolprovides-calibrating means Vfor varying the maximum ambient ltemperature at which -com- V-`l5r1a|sion, `is fl'rovided.

While 'tlievention has been disclosed'in 'alc- I'ns fjeeehiio '8 'cordance with vthe provisions or the patent statutes, fit in `vbe "understood 'that various fehanges inthe structural idetails and arrangement of parts -thereo may be made without departing from some -of the essential features of 'the invention.

' "claim as vmy invention:

l. Vil (circuit breaker having relatively movable contact 'mea-ns and operati-ng means 'releasable kto'eif'e'c't autom'atic'o'pening df saidco'ntact means, v'a trip `device comprising a trip member 4movable to release 'saidlo'perating means, a current -re- `sponsve bimetal element 'heated in response to the current -of lthe circuit, an ambient tempera- 'ture responsive 1'bimetal element mounted on `said movable trip member for compensating said cur rent responsive A'bimetal element for changes in ambient temperature, ac'ljus'ting 'means Jon Eone oi said bimetalielements "for varying the 'tripping "point of said trip device, said adjusting -means 'cooperating with the other of said bimetal elements upon thermal bending -of v'said current responsive'bimetalelement to move said trip member and eiect release of said `'operating "means,

' and stop 'means on said movable trip member 'for limiting the "amount of Acompensation `provided "by said ambient -temperature responsive bimetal element.

2. A circuit breaker having relatively fmovable contact 'means 'and Aoperating 'means releasableto eie'ct automatic opening'of said 'contact'm'ean's. a 'tripdevice comprisinga trip mem- 'ber movable'to release said voperating means, a

ilection of 'said ambient 'temperature vresponsive bimetal'to `therebylimit the amount Vof compensation, 'a'nd -nieans on said `current responsive vbimetal 'element 'for engaging `said ambient "ternperature responsive bimetal element upon thermal 'bending 'of "said current responsive bimetal 'element'to move said trip bar andei'rect release bimetal element rigidly mounted on said v'pivoted trip member, said ambient temperature responsive bimetal "element defleoting'in response 'to 'changes "in ambient 'temperature to "compensate said current responsive Vbimetal element, stop means on said 'pivotedtrip member for :limliting the deection of said 'ambient temperature responsive bimetal element, and said current responsive bimetal "element rvvhenheated a predetermined amount bending in "a direction 'to move said ambient'temp'erature responsive'bimetal "element to 'thereby cause pivotal movementbf 'said pivoted trip member and release of said releasabl'e means.

Vcircuit breaker `having relatively movable'contactme'ans and means releasableto effect automatic opening o'f'said `contactrmeans, a plv- 'ot'ei trip member movable to release said 'releasable means, a current responsive bimetal element disposed to be heated by the current of the circuit, an ambient temperature responsive bimetal element rigidly mounted on said pivoted trip member, said ambient temperature responsive bimetal element deflecting in response to changes in ambient temperature to compensate said current responsive bimetal element, stop means on said pivoted trip member for limiting the deflection of said ambient ternperature responsive bimetal element, calibrating means adjustable to vary the limiting point of said stop means, and said current responsive bimetal element when heated a predetermined amount bending in a direction to move said ambient temperature responsive bimetal element to thereby cause pivotal movement of said pivoted trip member and release of said releasable means.

5. A circuit breaker having relatively movable contact means and means releasable to effect automatic opening of said contact means, a trip device comprising a trip member movable to release said releasable means, a current responsive biinetal element heated by the current of the circuit, an ambient temperature responsive bimetal element mounted on said trip member, said ambient temperature responsive bimetal element defiecting in response to changes in arnbient temperature to compensate said current responsive bimetal element for changes in ambient temperature, means comprising a stop member on said trip member for limiting the deilection of said ambient temperature responsive bimetal element in response to an increase in ambient temperature, adjusting means on said stop means for varying the point at which said stop means limits the deflection of said ambient temperature responsive bimetal element, and an adjusting screw on said ambient vtemperature responsive Vbimetal element for varying the tripping point'of said current responsive bimetal element, said adjusting screw being engageabe by said current responsive bimetal element upon thermal bending of the latter to actuate said trip member and release said releasable means.

6. A circuit breaker having relatively movable Contact means and means releasable to effect automatic opening of said contact means, a trip device comprismg a trip member rotatable to release said releasable means, a current responsive bimetal element heated by the current of the circuit, said bimetal element having one end supported and the other end free, an ambient temperature bimetal element having one end secured to said trip member and having its free end disposed adjacent said free end of the current responsive bimetal, said ambient temperature responsive bimetal element deflecting in response to changes in ambient temperature to compensate said current responsive bimetal element, limiting means on said trip member for limiting the deiiec'tion of said ambient temperature bimetal element, and thermal bending of said current responsive bimetal element causing its free end to move said ambient temperature responsive bimetal element and rotate said trip member to effect release of said releasable means.

7. A circuit breaker having relatively movable contact means and means releasable to effect automatic opening of said lcontact means, a trip member operable to release said releasable means, a current responsive bimetal element heated by the current of the circuit, said bimetal element having one end supported and the other end free, an ambient temperature bimetal element having one end supported on said trip member on the side thereof away from said current responsive bimetal element, said ambient temperature responsive bimetal element extending to the opposite side of said trip member and having a reverse bend so that the free end thereof is disposed adjacent the free end of said current responsive bimetal element, said ambient temperature responsive bimetal element deflecting in response to changes in ambient temperature to compensate said current responsive bimetal element, ya projection on said trip member for limiting the deflection of said ambient temperature responsive bimetal element, and thermal bending of said current responsive bimetal element -causing its free end to move said ambient temperature responsive bimetal element and operate said trip member to release said releasable means.

8. A circuit breaker having relatively movable contact means and means releasable to effect opening of said contact means, a trip member operable to release said releasable means, a current responsive bimetal element having one end supported and the other end free and extending along one side of said trip member, an ambient temperature responsive bimetal element having one end supported on said trip member on the side thereof away from said current responsive bimetal element, said ambient temperature responsive bimetal element deflecting in response to changes in ambient temperature to compen- 'sate said current responsive bimetal element, a stop member on said trip member for limiting the deflection of said ambient temperature responsive bimetal element, and one of said bimetal elements having its free end cooperating with the free end of the other of said bimetal elements upon thermal bending of said current responsive bimetal element to actuate said trip member and release said releasable means.

9. A multi-pole circuit breaker having relatively movable contacts for each pole, operating mechanism releasable to effect automatic opening of said contacts, a trip member common to all of said poles operable to effect release of said operating mechanism, a thermally responsive bimetal element for each pole disposed to be heated in response to the current of the circuit of the associated pole, an ambient temperature respon- Isive bimetal element for each pole, each of said ambient temperature responsive bimetal elements being mounted on said trip member, stop means for each of said ambient temperature responsive bimetal elements for limiting the deflection of said ambient temperature responsive bimetal elements, adjusting means on one of said bimetal elements in each pole, said adjusting means upon thermal bending of the current responsive bimetal element cooperating with the other bimetal element in its associated pole to operate said trip member and effect release of said operating mechanism.

10. A multi-pole circuit breaker having relatively movable contacts for each pole, operating means releasable to effect automatic opening of said contacts, a trip member common to all of said poles operable to effect release of said operating means, a thermally responsive bimetal element for each pole disposed to be heated in response to the current of the circuit of the associated pole, an ambient temperature responsive bimetal element for each pole, said ambient temperature bimetal elements being rigidly mounted on said trip member, means on said trip member for limiting the deflection of the ambient temperature responsive bimetal elementA for each pole, means on each of said current responsive bimetal elements engagea/ble with the ambient temperature responsive bimetal element for the associated pole upon thermal bending of said thermally responsive bimetal element to operate said trip member and effect release of said operating means.

1l. A multi-pole circuit` 'breaker having relatively movable contacts for each pole, operating mechanism releasable to effect automatic opening of said contacts,` a trip member common to all of said poles operable to effect release of said operating mechanism, a thermally responsive bimetal element for each pole disposed to be heated by the current of the circuit of the associated pole, an ambient temperature responsive bimetal element for each pole rigidly mounted on said common trip member, limiting means on said common trip member for lifting the deflection of said ambient temperature responsive bimetal element for each. pole, means on said ambient temperature responsive bimetal element for each pole engagea-ble by the thermally responsive bimetal element of the associated pole upon thermal bending of said thermally responsive bimetal element to operate said trip member and eiect release of said operating means.

12. A circuit breaker having relatively. movable contact means and means releasable to effect automatic opening of said contact means, a trip device comprising a trip member movable to release said releasable means, a current responsive bimetal trip element heated in response to the current of the circuit, an ambient temperature responsive bimetal element mounted on said trip member, a stop member on said trip member for limiting the deflection of said ambient temperature responsive bimetal element, an insulating member on one of said bimetal elements, and said insulating member cooperating with the other of said bimetal elements upon thermal bending of said current responsive bimetal element to move said trip member and effect release of said releasable means.

13. A circuit breaker having relatively movable contact means and means releasable. to effect automatic opening of said contact means, a trip device comprising a trip member movable to effect release of said releasable means, a current responsive bimetal element heated by the current of the circuit, an ambient temperature responsive bimetal element rigidly mounted on said trip member, means comprising a projection on said trip member for limiting the deflection of said ambient temperature responsive bimetal element, adjusting means mounted on said ambient temperature responsive bimetal element, and insulating means on said adjusting means engageable by said current responsive bimetal element upon thermal bending of the latter to move said trip member and cause release of said releasable means.

14. A circuit breaker having relatively movable contact means and means releasable to effect automatic opening of said contact means, a trip member operable to release said releasable means. a current responsive bimetal element having one end supported and the other end free and extending along one side of said trip member, an ambient temperature responsive bimetal element having one end rigidly supported on said trip member on the side thereof away from said current responsive bimetal element, stop means on said trip member for limiting the deection of said ambient temperature responsive bimetal element, and adjusting means mounted at the free end of one of said bimetal elements having an insulating member thereon cooperating with the free end of the other of said bimetal elements upon thermal bending of said current responsive bimetal element to operate said trip member and cause release of said releasable means.

HILLER D. DORFMAN.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,214,695 Jennings Sept. 10, 1940 2,416,163 Dyer et al. Feb. 18, 1947 2,455,753 Getchell Dec. '7, 1948