US3566318A

US3566318A - Circuit breaker with improved trip means

Info

Publication number: US3566318A
Application number: US788230A
Authority: US
Inventors: Francis L Gelzheiser; Charles E Nystrom
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1968-12-31
Filing date: 1968-12-31
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23
Also published as: BR6915728D0; FR2027484A1; ES374717A1; GB1258828A

Abstract

A CIRCUIT BREAKER COMPRISES IMPROVED THERMAL AND ELECTRO-MAGNETIC TRIP MEANS FOR AUTOMATICALLY TRIPPING THE CIRCUIT BREAKER UPON THE OCCURRENCE OF OVERLOAD CURRENT CONTIONS. AUTOMATIC THERMAL CALIBRATION IS BUILT INTO THE CONSTRUCTION WHEREBY CIRCUIT BREAKERS CAN BE MANUFACTURED IN QUANTITY WITH PREDICATABLE TRIPPING CHAR-

ACTERISTICS. A LEVER LATCH MEMBER, WHICH IS SECURED TO A BIMETAL MEMBER, IS ANGLED AGAINST RELEASABLE MEMBER WITH A LEVERING ACTION, UPON FLEXING OF THE BIMETAL MEMBER, TO RELEASE THE RELEASABLE MEMBER TO THEREBY TRIP THE CIRCUIT BREAKER.

Description

Feb. 23, 1971 F. L. GELZHEQISEYR ETAL 3,566,318

CIRCUIT BREAKER WITH IMPROVED TRIP MEANS. Filed Dec; '51,. 1968 gsheets-s eet 1 v WITNESSES: v INVENTORS Francis L. Gelzheiser and fi h Chorles E. Nys trom.

ATTORNEY ahwil $541M b- 3, 19.71 F. L. GELZHEISER ETAL 3,566,318

CIRCUIT BREAKER WITH IMPROVED TRIP MEANS Filed Dec--. 51, 1968 2 Sheets-Sheet 2 FIG. 2.

United States Patent 01' fice 3,566,318 CIRCUIT BREAKER WITH IMPROVED TRIP MEANS Francis L. Gelzheiser, Fairfield, and Charles E. Nystrom,

Derby, Conn., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 31, 1968, Ser. No. 788,230

Int. Cl. H01h 73/48 I US. Cl. 335-39 20 Claims ABSTRACT OF THE DISCLOSURE A circuit breaker comprises improved thermal and electro-magnetic trip means for automatically tripping the circuit breaker upon the occurrence of overload current conditions. Automatic thermal calibration is built into the construction whereby circuit breakers can be manufactured in quantity with predictable tripping characteristics. A lever latch member, which is secured to a bimetal member, is angled against a releasable mem ber with a levering action, upon flexing of the bimetal member, to release the releasable member to thereby trip the circuit breaker.

BACKGROUND AND OBJECTS OF THE INVENTION In the manufacture of circuit breakers, it is common practice to calibrate each individual breaker so that the breaker willpredictably trip within a predetermined time span at a predetermined sustained overload current. In many cases each breaker is calibrated by adjustment of a calibrating screw or bending of a part to adjust the amount of latch engagement between a releasable member and the trip device. In some cases, a calibrated breaker can fall out of calibration under shock or other conditions that might vary the amount of latch engagement.

An object of this invention is to advance the art by providing a novel circuit breaker that is so constructed and arranged that the breaker is automatically calibrated merely by the assembly operation.

Another object of this invention is to provide an improved circuit breaker that is less likely to fall out of calibration during use of the breaker.

Another object of this invention is to provide a circuit breaker with improved dependable thermal tripping characteristics.

A further object of this invention is to provide a circuit breaker with improved thermal and magnetic trip means.

A general object of this invention is to provide an improved circuit breaker that is relatively easy to assemble and dependable in operation.

SUMMARY OF THE INVENTION A circuit breaker comprises a pair of contacts and a latched releasable member movable when released from an initial latched position to a tripped position to effect opening of the contacts. The releasable member is latched by trip means which comprises an elongated bimetal that is supported at the upper end thereof on a flat spring member which is in turn supported on a fixed support. An elongated rigid member, having a window-opening therein to provide a latch surface thereon, is welded or otherwise fixedly secured to the bimetal inproximity to the lower or free end of the bimetal. The releasable member is movably supported at the one end thereof and comprises a latch part at the other end thereof that protrudes into the window-opening of the latch member to rest on the latch surface of the latch member. The supporting 3,566,318 Patented Feb. 2.3, 1971 spring biases the bimetal and latch member toward the releasable member with a fulcrum part or stop part on the releasable member engaging a stop part of the latch member above the window opening. With the spring member biasing the latch member into engagement with the releasable member at a predetermined angle, the amount of latch engagement between the latch member and the releasable member is predetermined and circuit breakers can be produced in quantity with each breaker having the predetermined amount of latch engagement. The latch member, which is fixed at the lower end thereof to the lower end of the bimetal, extends upward along the high-expansion side of the bimetal in a parallel relationship with the bimetal. The bimetal is connected to carry current in the circuit breaker. Upon the occurrence of a sustained lesser overload above a first predetermined value, the bimetal will flex carrying the lower end of the latch member away from the releasable member and, with the spring support biasing the bimetal and latch member toward the releasable member, this movement will produce a levering action between the stop part of the latch member and the fulcrum or stop part on the releasable member during which levering action the latch surface of the. latch mem-v ber will release the releasable member to effect a tripping operation. With the latch member levering against a fulcrum part on the releasable member, by properly positioning the angle of the latch member and bimetal relative to the releasable member and by properly selecting the bimetal, the amount of unlatching movements of the latch surface of the latch member can be predetermined so long as the supporting spring maintains abias of the stop part of the latch member against the fulcrum part of the releasable member. The supporting spring member is selected such that it is strong enough to maintain the bias of the latch member against the fulcrum part of the releasable member yet not so strong as to flex the bimetal in the cold or normal position which flexing could affect the thermal trippingcharacteristics. With the amount of latch engagement between the releasable member and latch member predetermined and built into the breaker, and with the predetermined predictable amount of unlatching movement of the latch surface in response to predetermined currents built into the breaker,- it can be understood that the breakers can be manufac-- tured in quantity with predetermined thermal tripping characteristics built into the breakers. In the preferred embodiment, the elongated latch member is a magnetic armature, and a magneic member is supported in the breaker in a spaced relationship from the armature so that upon the occurrence of a severe overload current above the second predetermined value the armature will be instantaneously attracted to the other magnetic member to eflect a magnetic tripping operation. During magnetic tripping operations, the supporting spring flexes to permit quick unitary movement of the bimetal and armature to the magnetically-tripped position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an end view of a double-type circuit breaker constructed in accordance with principles of this invention;

FIG. 2 is a sectional view, on an enlarged scale relative to FIG. 1, taken generally along the line II-II of FIG. 1. The circuit breaker is shown in FIG. 2 in the on or closed position.

FIG. 3 is a view similar to FIG. 2 with the breaker being shown in the off or open position;

FIG. 4 is a view similar to FIGS. 2 and 3 with the parts shown at the instant that a magnetic tripping operation is completed;

FIG. is a view of parts of the breaker shown in FIGS. 24 with the parts being shown in a position reached during a thermal tripping operation;

FIG. 6 is a view similar to FIG. 5 illustrating another embodiment of the invention with the parts being shown in the latched position;

FIG. 7 is a view of the parts shown in FIG. 6 during a thermal tripping operation;

FIG. 8 is a view similar to FIG. 6 illustrating still another embodiment of the invention; and

FIG. 9 is an end view of the armature and part of the bimetal of FIGS. 24 illustrating the window-opening in the armature.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, there is shown therein a double-type circuit breaker 9 comprising a molded insulating housing that comprises two

insulating parts

11 and 13 forming two compartments. Each of the

parts

11 and 13 comprises a back portion molded integral with four sides forming an open front. The open front of the part 11 is covered by the back portion of the part 13, and the open front of the part 13 is covered by an insulating cover 15. The three

parts

11, 13 and 15 of the housing are held rigidly together by three rivets 17 (FIGS. 2-4).

The

housing parts

11 and 13 form two independent compartments housingtwo circuit breaker mechanisms which, except for a line terminal structure that will be hereinafter described, are of identical construction and operation with each mechanism operating independently of the other. For this reason, only the mechanism enclosed by the housing part 13 will be specifically described, it being understood that, unless otherwise mentioned, the description applies toboth mechanisms of the double-type circuit breaker.

1 Referring to FIG. 2, the circuit breaker mechanism which is enclosed by the housing part 13 comprises a stationary contact 21, a cooperating movable contact 23, a supporting metal frame 25, an operating mechanism 27 and a trip device 29.

. The stationary contact 21 is welded, or otherwise secured, to a line terminal 31 that is exposed at an opening 35 (FIG. 1) to cooperate with a symmetrically constructed line terminal 37 that is a part of the mechanism supported in the housing part 11. The line terminals 31 and 37 are independent in that each is a part of a separate independently functioning circuit breaker mechanism. The terminals 31 and 37 are resiliently biased to engage opposite sides of a blade or stab in a load center when the double-type breaker is mounted in the operating position.

Referring to FIGS. 2-4, the stationary contact 21 cooperates with the movable contact 23 that is welded or otherwise secured to a small flange portion of a flat metallic generally C-shaped contact arm 41. Means for operating the contact arm 41 to the open and closed positions comprises an operating member indicated generally at 43 having a V-shaped opening 45 therein, which opening receives a projection 47 of the stationary metallic frame 25. The operating member 43 is biased outwardly or upward as seen in FIGS. 2-4, by means to be hereinafter described, to a position wherein the lower edges of the projection 47 pivotally engage the lower side walls of the V-shaped opening 45. The contact arm 41 is bent over at its upper end at 48, and a slot is provided in the part 48. Depressions 51 are formed in the part 48 on opposite sides of the slot. When the parts are in operating position, a projection molded integral with the operating member 43 extends into the slot of the contact arm 41 to position the operating member 43 relative to the contact arm 41, and pivoting portions 55 on opposite sides of the projection pivotally engage in the depressions 51 .of the contact arm 41. The operating member 43 has a 4 handle portion 57 molded integral therewith which extends through an opening 61 in the housing whereby the mechanism may be manually operated to open and close the breaker. Arcuate surfaces 63 on opposite sides of the handle 57 substantially close the opening 61 in all positions of the operating member 43. Motion is transmitted from the operating member 43 to the contact arm 41 when the breaker is manually operated and from the contact arm 41 to the operating member 43 when the breaker is automatically tripped.

The frame 25 supports an insulating pivot 65. A releasable member 67 is pivotally supported at one end thereof on the pivot 65. The other end 69 of the releasable member 67 is latched by the trip device 29 in a manner to be hereinafter specifically described. Except for the trip device 29, the operating mechanism is more specifically described in the patent to F. L. Gelzheizer Pat. No. 3,254,176.

As is more specifically described in the above-mentioned Pat. 3,254,176, the ends of the releasable member 67 are offset and disposed along a plane which is parallel to a plane in which the main body portion of the releasable member 67 is disposed. A spring 71 is connected, under tension, at one end ina slot 73 in contact arm 41, and at the other end in a slot in a projection 75 that extends from the main body portion of the releasable member 67.

The contact arm 41 is electrically'connected to the lower end of a bimetal 77 by means of a flexible conductor 79. The bimetal 77 is part of the trip device 29 that will be hereinafter described. A flexible conductor 81 connects the upper end of the bimetal 77 with a terminal strap 83 that extends through an opening in the end wall of the circuit breaker. A terminal connector 85 is connected to the external end of the terminal strap 83 to permit connection of the circuit breaker in a circuit in a manner well known in the art. The closed circuit through the circuit breaker 9 extends from the terminal 31 through the stationary contact 21, movable contact 23, contact arm 41, flexible conductor 79, current-carrying bimetal 77, flexible conductor 81, terminal strap 83, to a conducting line that would be connected to the terminal strap 83 by means of the terminal connector 85. Since the movable contact arm 41 extends downwardly from its pivot, the arc is established adjacent the bottom of the housing in an arc chamber 87 which is connected by a vent passage 89 to an opening in the end of the housing beneath the terminal connector 85.

When the releasable member 67 is in the latched position shown in FIGS. 2 and 3, the circuit breaker may be manually operated by operation of the operating member 43. Movement of the operating member 43 in a clockwise direction from the on or closed position seen in -FIG. 2 to the off or open position seen in FIG. 3 carries the upper end of the contact arm 41 to the left of the line of action of the spring 71 whereupon the spring acts to move the contact arm 41 with a snap action to the open position seen in FIG. 3. As can be understood with reference to FIGS. 2 and 3, the spring 71 biases the contact arm 41 upward into engagement with the operating member 43 to bias the operating member 43 against the lower edges of the projection 47 about which the operating member 43 pivots. Movement of the op erating member 43 in a counterclockwise direction from the off position seen in FIG. 3 to the on position seen in FIG. 2 moves the upper end of the switch arm to the right of the line of action of the spring 71 to move the contact arm 41 to the closed position seen in FIG. 2.

The trip device 29 comprises the elongated bimetal 77. The bimetal 77 is a flat member that is secured at the upper end thereof to a flat leaf spring 91 that is secured to a proejction 93 of the stationary frame 25. The frame 25 is a flat member that is secured in place in the housing between projections of the molded insulating housing, and the projection 93 is bent over to extend and in a direction generally normal to the plane of the flat supporting plate 25. The flat spring is fixedly secured to the projection 93 to support the bimetal 77. An elongated rigid magnetic armature latch member 95 is welded, at 97 to the high expansion side of the bimetal 77. The armature 95 extends upward along the high expansion side of the bimetal 77 in a parallel relationship with the bimetal 77 when the bimetal is in the cold or straightened condition. As can be seen in FIG. 9, the armature 95 has a window opening 99 therein to form a latch surface 101 at the base of the opening 99. As can be seen in FIGS. 4 and 5, the latch end 69 of the releasable member 67 is formed with a latch surface 103 there on and a stop surface or fulcrum part 105 thereon. A surface portion 1'07 (FIG. 4) of the armature 95 serves as a stop part to engage the fulcrum part 105 of the releasable member 67 in the latched position of the releasable member. A rigid magnetic member 109 is supported in the

housing

13, 15 between insulating portions 111 of the housing 13 which form slots in which the magnetic member 109 is positioned. The projections 111 (FIG. 4) limit movement of the magnetic member 109 in the plane of the paper as seen in FIG. 4, and the

housing parts

13, 15 limit movement of the magnetic member 109 in a direction normal to the plane of the paper.

The circuit breaker is shown in FIG. 2 in the reset position wherein the releasable member 67 is latched on the armature 95. The circuit breaker can be manually operated only when the releasable member 67 is in the reset or latched position. In the position seen in FIG. 2, the supporting spring 91 biases the bimetal 77 to the left toward the releasable member 67 which movement is limited by the engagement of the stop part 107 of the rigid armature 95 with the stop part or fulcrum part 105 of the rigid releasable member 67. In this position, the latch surface 103 of the releasable member 67 rests on the latch surface 101 of the armature 95 to latch the releasable member 67 preventing clockwise movement of the releasable member 67 about the pivot 65. The high expansion side of the bimetal 77 is on the left as seen in FIG. 2. Upon the occurrence of a sustained lesser overload current above a first predetermined value, the bimetal 77, which is heated by the current flowing therethrough, deflects from the position seen in FIG. 2 to the thermally-tripped position seen in FIG. 5. The bias of the spring 91 of the complete bimetal 77 toward the left is such that the spring 9 1 maintains the bias of the part 107 of the armature 95 against the fulcrum part 105 of the releasable member 67 during the deflection of the bimetal 77 to the thermally-tripped position. The bimetal 77 deflects to a curvature such as that shown in FIG. during which movement the rigid armature 95 is angled to the position seen in FIG. 5 with the lower end of the rigid armature 95 being carried by the lower end of the bimetal 77, and the armature 95 moves about the fulcrum part 105 with a levering action to move the latch surface 101 of the armature 95 free of the latch surface 103 of the releasable member 67 to thereby release the releasable member 67. When the releasable member 67 is released, the spring 71 acts to rotate the releasable member 67 in a clockwise direction about the pivot 65 until the releasable member 67 is stopped by engagement thereof with a molded projection 117 on the housing part 13. During this movement, the line of action of the spring 71 moves to the right of the

pivot

55, 51, whereupon the spring 71 biases the contact arm 41 in opening direction and moves the contact arm 41 so that the line of action of the force exerted by the spring on the operating member 43 shifts across the

pivot

45, 47 and actuates the operating member 43 to the tripped position shown in FIG. 4. The tripped position of the operating member 43 is intermediate the on and off positions. The operating member 43 is stopped in the intermediate or tripped position seen in FIG. 4 when an insulating projection 119 thereon engages the projection 75 on the releasable member 67. The contact arm 41 is stopped in the open position seen in FIG. 4 when it engages an insulating projection 121 molded integral with the housing part 13. Positive separation of the contacts is provided during a tripping operation by means of a projection 123 extending from the releasable member 67 If the contacts are slow in opening due to sticking, drag or other reasons, the projection 123 engages the inner edge of the contact arm 41 to start the contact arm in opening direction.

The circuit breaker is trip-free in that the breaker will automatically trip open even if the handle 57 is held in the closed position.

Following a tripping operation, it is necessary to reset the breaker before the breaker can be operated. This is accomplished by moving the operating member 43 from the tripped position (FIG. 4) slightly beyond the full off position. During this movement, the projection 119 on the operating member 43 operates against the projection 75 of the releasable member 67 to move the releasable member 67 counterclockwise to a position wherein the latch surface 103 of the releasable member 67 is just above the latch surface 101 of the armature whereupon the spring 91 moves the bimetal 77, which cools and straightens when in non-current carrying tripped condition, and armature 95 toward the releasable member to latch the trip member in the initial operating position shown in FIG. 3. With the releasable member 67 reset in the operating position, the circuit breaker can be manually operated in the same manner as was hereinbefore described.

The circuit breaker is instantaneously tripped upon the occurrence of a short circuit or severe overload current above a second predetermined value, higher than the first predetermined value, by operation of the magnetic trip of the trip means 29. As can be understood with reference to FIGS. 2 and 9, the current passing through the bimetal 77 generates magnetic flux which operates through the armature 95, the air gaps between the armature 95 and the magnetic member 109, and through the stationary magnetic member 109. When the current reaches the second predetermined value, this magnetic flux is strong enough to attract the armature 95 toward the stationary magnetic member 109, and the spring 91 flexes permitting the armature 95 and bimetal 77 to move as a unit to the magnetically-tripped position seen in FIG. 4 wherein the releasable member 67 is released to trip the breaker in the same manner as was hereinbefore described. Following a magnetic tripping operation, the circuit breaker is reset and relatched in the same manner as was hereinbefore set forth with regard to the time-delay thermal tripping operation. The bimetal 77 and armature 95 are shown in the attracted position in FIG. 4. It can be understood that when the circuit is interrupted the armature 95 will no longer be attracted to the stationary magnetic member 109 and the spring 91 will return the bimetal 77 and armature 95 to the unattracted position.

Another embodiment is shown in FIGS. 6 and 7 where the same reference characters are used with the reference character being primed to indicate the different position of the stop part or fulcrum part 105' on the releas able member 67, and with the reference character -107 being primed to indicate the different position of the stop part 107' on the armature. The releasable member is shaped differently to reposition the fulcrum part 105'. Otherwise, the parts shown in FIGS. 6 and 7 would be used in a circuit breaker of identical construction to that hereinbefore described with reference to FIGS. 15. As can be seen in FIGS. 6 and 7, the shape of the releasable member 67 has been modified to provide a greater distance between the latch surface 103 and the fulcrum part 105. This construction provides a longer lever arm to thereby provide increased unlatching movement of the latch surface 101 during thermal tripping operations.

Another embodiment of the invention is shown in 'FIG. 8 wherein the reference characters and parts are the same as those shown in FIGS. 6 and 7 with the exception that the reference character 107 is double primed and applied to a bump or projection on the face of the armature 95. In the same breaker frame sizes, various latch engagements may be necessary for different ratings. The amount of latch engagement between the latch surface 103 of the releasable member 67 and the latch surface 101 of the armature 95 can be controlled by means of the projection 107" that can be provided as a variable projection manufactured with the armature 95. Another way of varying the amount of latch engagement would be to keep the manufacture of the armature 95 constant and varying the shape of the releasable member 67 to position the stop part 105' to thereby control the amount of latch engagement.

If for some foreseen reason breakers should fall out of calibration, and this would be under exceptional circumstances, then correction could be made by slightly adjusting the armature and bimetal. In order to cause the breaker to trip sooner by providing less latch engagement, a tool such as a screwdriver blade could be placed between the bimetal and the upper portion of the armature 95, and the blade could be rotated to Wedge the upper portion of the armature 95 away from. the bimetal to thereby reduce the amount of latch engagement between the latch surface 103 of the releasable member 67 and the latch surface 101 of the armature. Reversing the process with a pair of pliers or other type of tool by squeezing the upper end of the armature 95 toward the bimetal 77 would increase the amount of latch engagement between the releasable member 67 and bimetal 77 to cause the breaker to trip with a longer time delay.

From the foregoing, it can be understood that there is provided by this invention a circuit breaker with improved trip means. The latch surface 103 and fulcrum part 105 of the releasable member 67 are positive die cuts which will remain constant during the life of the die that is used in the manufacture of the releasable member 67. The latch surface 101 and stop portion 107 on the armature 95 are positively determined by the manufacture of the armature 95. With the

surfaces

103, 105 on the releasable member 67 and the

surfaces

101, 107 on the armature 95 predetermined and fixed, it can be understood that so long as the armature 95 is biased against the releasable member 67 at a predetermined angular position, the amount of latch engagement between the releasable member 67 an armature 95 will be predetermined and constant. Thus, the circuit breakers can be manufactured in quantity with a predetermined amount of latch engagement. With the spring 91 biasing the bimetal 77 to maintain the bias of the armature 95 (at 107) against the fulcrum part 105 of the releasable member 67, as the bimetal 77 flexes the lower end of the bimetal will carry the lower end of the armature to the right (FIG. and the deflection of the bimetal will cause the armature 95 to angle against the fulcrum part 105 of the releasable member 67 with a levering action to release the releasable member 67. It can be understood that by providing a predetermined angular position of the bimetal 77 and armature 95 relative to each other and relative to the releasable member 67, the tripping characteristics of the circuit breaker can be predetermined by maintaining the bias of the armature 95 against the fulcrum part 105 of the releasable member 67 and by selecting the bimetal 77 with predetermined flexing characteristics. Thus, by the proper selection, construction and arrangement of the

parts

67, 95, 77, 91, predetermined tripping characteristics can be built into the breaker during the manufacture of the breaker, and self-calibrated breakers can be manufactured in quantity without requiring calibration after assembly, and without requiring additional parts such as the calibrating screws that have been used in some prior art breakers. The supporting spring 91 should be strong enough to maintain the bias of the armature 95 against the releasable member 67 during tripping operations yet not so strong as to cause a physical deflection of the bimetal 77 in the cold position of the bimetal which physical deflection could affect the thermal tripping characteristics. The improved trip device also comprises the magnetic trip which operates to move the armature and bimetal as a unit toward the stationary magnetic member during which movement the supporting spring 91 flexes so that the more rigid bimetal need not be flexed by the pull of the armature during magnetic tripping operations.

We claim as our invention:

1. A circuit breaker comprising a pair of contacts, a releasable member comprising a first latch surface, a latch member comprising a support part and a stop part and a second latch surface, a bimetal member for moving said latch member in response to current flow, said latch member at said support part being mounted on said bimetal member, resilient biasing means biasing said bimetal member to effect a bias of said latch member into latching engagement with said releasable member in which latching engagement said second latch surface latches against said first latch surface, said releasable member said latch member said bimetal member and said resilient biasing means being constructed and arranged such that upon flexing of said bimetal member said bimetal member carries said support part of said latch member away from said releasable member while said resilient biasing means effects a bias of said stop part of said latch member against said releasable member until said second latch surface disengages from said first latch surface whereby a predetermined unlatching movement of said second latch surface is provided relative to said first latch surface upon the occurrence of a predetermined flexing of said bimetal member in response to current flow, upon the occurrence of a sustained lesser overload current above a predetermined value said bimetal member flexing to move said latch member to thereby move said second latch surface relative to said first latch surface to an unlatching position to thereby release said releasable member, and means operating upon release of said releasable member to effect opening of said contacts.

2. A circuit breaker according to claim 14, said first latch member being an armature latch member of magnetic material, a separate magnetic member separate from said armature magnetic member, means supporting said armature latch member and said, separate latch member such that said armature latch member is magnetically attracted to said separate magnetic member upon the occurrence of overload current conditions above a second predetermined value, and upon the occurrence of overload current conditions above said second predetermined value said armature latch member being attracted toward said separate magnetic member to release said releasable member.

3. A circuit breaker according to claim 2, said bimetal member being an elongated bimetal member, said resilient biasing means comprising resilient support means supporting said elongated bimetal member in proximity to one end of said elongated bimetal member, said armature latch member comprising an elongated rigid armature latch member fixedly supported at one end thereof in proximity to the other end of said elongated bimetal member and extending along side said elongated bimetal member on the high expansion side of said elongated bimetal member, said resilient support means biasing said bimetal to bias said armature latch member against said releasable member to provide a predetermined amount of latch engagement between said first and second latch surfaces, upon the occurrence of said lesser overload current above said first predetermined value said elongated bimetal member flexing to carry said one end of said armature latch member away from said releasable member and to angle said armature latch member against said releasable member at said stop part under the bias of said resilient support means to thereby move said second latch surface relative to said first latch surface to an unlatching position to release said releasable member, and

upon the occurrence of said overload current above said second predetermined value said armature latch member being attracted to said separate magnetic member to move said armature latch member and elongated bimetal member as a unit to an unlatching position to release said releasable member which unitary movement is permitted by the flexing of said resilient support means.

4. A circuit breaker according to claim 3, means connecting said elongated bimetal member as a current carrying bimetal member in the circuit of said breaker, and upon the occurrence of said overload current above said second predetermined value the current in said elongated bimetal member generating magnetic flux in a magnetic circuit through said armature latch member and said separate magnetic member to effect attraction of said armature latch member toward said separate magnetic member to effect release of said releasable member.

5. A circuit breaker according to claim 1, said latch member at said support part being fixedly mounted on said bimetal member, said releasable member said latch member said bimetal member and said biasing means being constructed and arranged such that upon flexing of said bimetal member said bimetal member carries said fixedly mounted support part of said latch member away from said releasable member While said biasing means biases said bimetal to effect a bias of said stop part of said latch member against said releasable member until said second latch surface disengages from said first latch surface,

6. A circuit breaker according to claim 5, said first latch member being an armature latch member of magnetic material, a separate magnetic member separate from said armature latch member, means supporting said armature latch member and said separate magnetic member such that said armature latch member is magnetically attracted to said separate magnetic member upon the occurence of overload current conditions above a second predetermined value, and upon the occurrence of overload current conditions above said second predetermined value said armature latch member being attracted toward said separate latch member moving said bimetal member and said armature latch member as a unit to release said releasable member.

7. A circuit breaker according to claim 6, means connecting said bimetal member as a current carrying bimetal member in the circuit of said circuit breaker, and upon the occurrence of said overload current above said second predetermined value the current in said bimetal member generating magnetic flux in a magnetic circuit through said armature latch member and said separate magnetic member to effect attraction of said armature latch member toward said separate magnetic member to effect release of said releasable member.

8. A circuit breaker according to claim 13, said rigid latch member being an armature latch member of magnetic material, a separate magnetic member separate from said armature latch member, said separate magnetic member and said armature latch member being supported such that said armature latch member is magnetically attracted to said separate magnetic member upon the occurrence of overload current conditions above a second predetermined value, and upon the occurrence of overload current conditions above said second predetermined value said armature latch member being attracted toward said separate magnetic member to move said armature latch member and bimetal member as a unit toward said separate magnetic member against the bias of said resilient means to release said releasable member.

9. A circuit breaker according to claim 8, said bimetal member having a high expansion side and a low expansion side, said armature latch member being carried on said bimetal member on the high expansion side of said bimetal member, said separate magnetic member being spaced from said armature latch member and bimetal member on the low expansion side of said bimetal member, means connecting said bimetal member to carry current in the circuit of said circuit breaker, said armature latch member and said separate magnetic member being supported such that the current in said bimetal member generates magnetic flux to cause attraction of said armature latch member toward said second magnetic member, and upon the occurrence of said overload current conditions above said second predetermined value said armature latch member being attracted to said separate magnetic member and moving as a unit with said bimetal member against the bias of said biasing means toward said separate magnetic member to release said releasable member.

10. A circuit breaker according to claim 9, said re silient biasing means being a spring member supported on a stationary support, said bimetal member being su ported and carried on said spring member whereby said bimetal member is resiliently mounted on said stationary support.

11. A circuit breaker according to claim 10, said spring member being a leaf spring member supported on said stationary support with said bimetal member being supported on said leaf spring member spaced from said stationary support whereby said bimetal member is resiliently mounted on said stationary support.

12. A circuit breaker comprising a pair of contacts, a releasable member movable when released from an initial position to a tripped position to effect opening of said contacts, a stationary support, a leaf spring member comprising a first support part secured to said stationary support, said leaf spring member comprising a second support part, an elongated bimetal member fixed to said second support part of said leaf spring member, a latch member carried on said bimetal member and being in a latching position latching said releasable member in said initial position, said leaf spring member biasing said bimetal member to thereby bias said latch member to said latching position, and upon the occurrence of certain overload current conditions said leaf spring member and said bimetal member operating to move said latch member against said releasable member with an angular levering movement to thereby move said latch member from said latching position to an unlatching position to release said releasable member.

13. A circuit breaker comprising a pair of contacts, a releasable member movable when released from an ini tial position to a tripped position to effect opening of said contacts, latch means in a latching position latching said releasable member in said initial position, resilient means biasing said latch member against said releasable member, and upon the occurrence of certain overload current conditions means operating to move said latch means against said releasable member with an angular levering movement to thereby move said latch means from said latching position to an unlatching position to release said releasable member, said latch means comprising a rigid latch member, a bimetal member carrying said rigid latch member, said resilient means biasing said bimetal member to thereby bias said rigid latch member against said releasable member, and upon the occurrence of sustained lesser overload current conditions above a first predetermined value said bimetal member flexing to a tripped position during which flexing movement said biasing means biases said bimetal member to thereby maintain the bias of said rigid latch member against said releasable member to move said rigid latch member against said releasable member with said angular movement to provide a levering action of said rigid latch member against said releasable member to effect release of said releasable member.

14. A circuit breaker according to claim 13, and means operating upon the occurrence of an overload above a second predetermined value higher than said first prede termined value to move said rigid latch member rapidly to release said releasable member.

15. A circuit breaker comprising a stationary contact, a movable contact, a movable contact arm carrying said movable contact, a releasable member, trip means comprising a bimetal member and a lever latch member, said lever latch member comprising a support part, said lever latch member being fixedly secured to said bimetal member at said support part, said lever latch member being in a latching position latching said releasable member in an initial position, operating spring means, manually operable means operable when said releasable member is in said initial position to operate said operating spring means and move said movable contact arm to open and close said contacts, upon the occurrence of certain overload current conditions above a first predetermined value said bimetal member flexing to angle said lever latch member against said releasable member with a levering action to thereby release said releasable member, and upon release of said releasable member said operating spring means operating to move said releasable member and said movable contact arm to a tripped position to open said contacts.

16. A circuit breaker according to claim 15, and electromagnetic trip means operating automatically upon the occurrence of overload current conditions above a second predetermined value higher than said first predetermined value to move said lever latch member to release said releasable member.

17. A circuit breaker according to claim 15, said breaker comprising a front and a back, said manually opperable means being positioned at the front of said breaker, an elongated bimetal member, spring support means supporting said elongated bimetal member at the front of said elongated bimetal member, said lever latch member comprising an elongated member, means fixedly securing said lever latch member in proximity to the back of said latch member to said bimetal member in proximity to the back of said bimetal member on the high-expansion side of said bimetal member with said lever latch member extending frontward along side the high-expansion side of said bimetal member, said releasable member comprising a first latch surface and a fulcrum part which part is positioned frontward of said first latch surface, said lever latch member comprising a second latch surface and a stop part which stop part is disposed frontward of said second latch surface, said spring support means biasing said bimetal member toward said releasable member to a latching position wherein said stop part on said lever latch member engages said fulcrum part on said releasable member and wherein said second latch surface engages said first latch surface to latch said releasable member, upon the occurrence of a sustained lesser overload current above a first predetermined value said bimetal member being heated and flexing to move the back end thereof away from said releasable member and to angle said lever latch member against said fulcrum part of said releasable member with a levering action during which movement said spring support means biases said lever latch member against said fulcrum part of said releasable member and during which movement said second latch surface moves away from said first latch surface to release said releasable member; and upon release of said releasable member said operating spring means operating to move said releasable member to a tripped position to eifectmovement of said movable contact arm to open said contacts.

18. A circuit breaker according to claim 12, said lever latch member being an armature lever latch member of current above a second predetermined value higher than said first predetermined value said armature lever latch member being attracted to said separate magnetic member and moving with said bimetal member toward said separate magnetic member to release said releasable member.

19. A circuit breaker according to claim 10, means connecting said bimetal member to carry current in the circuit of said circuit breaker, and upon the occurrence of an overload above said second predetermined value the current in said bimetal member generating magnetic flux to cause said attraction of said armature lever latch member toward said separate magnetic member.

20. A circuit breaker according to claim 19, said spring support means comprising a flat leaf spring supported at one end thereof on a stationary support and being connected at the other end thereof to said bimetal member to support said bimetal member and to provide said bias of said bimetal member and said armature lever latch .member toward said releasable member.

References Cited .UNITED STATES PATENTS 2,360,684 10/1944 Jennings 335-36 2,996,589 8/1961 Myers 33748 3,110,786 11/1963 Gelzheiser 33537 HAROLD BROOME, Primary Examiner US. Cl. X.R. 335-23