US3453568A - Electric circuit breaker with improved auxiliary device - Google Patents

Description

July 1, 1969 F. H. MURPHY ET AL 3,453,568 ELECTRIC CIRCUIT BREAKER WITH IMPROVED AUXILIARY DEVICE Filed Dec. 20. 1967 Sheet Z of 2 INVENTORS FRANK r'v'. MURPHY, HENRY 5. Ou/n/ A T'TOkA/E Y y 1969 F. H. MURPHY ET AL 3,453,568

ELECTRIC CIRCUIT BREAKER WITH IMPROVED AUXILIARY DEVICE Filed Dec. 20, 1967 Sheet 2 M2 INVENTORS FRANK H MuRPm; HENRY E. 5. Owen A TT'ORA/E Y United States Patent 3,453,568 ELECTRIC CIRCUIT BREAKER WITH IMPROVED AUXILIARY DEVICE Frank H. Murphy, West Hartford, and Henry E. S. Owen,

Avon, Conn., assignors to General Electric Company, a

corporation of New York Filed Dec. 20, 1967, Ser. No. 692,172 Int. Cl. HOlh 83/12 US. Cl. 335-20 7 Claims ABSTRACT OF THE DISCLOSURE A circuit breaker auxiliary device including a springbiased tripping slide held against movement by a springbiased latching member, the latter being held in latching position against its spring-bias by a solenoid and released when the solenoids voltage drops sufficiently. The tripping movement of the circuit breaker moves the tripping slide to reset position whereby resetting of the circuit breaker, so as to permit subsequent reclosing, can occur only if the solenoid has sufficient voltage to hold the latching member in position to oppose the tripping movement of the tripping slide. In one form, the device functions as an undervoltage release device for sensing an undesirable drop in voltage. In another form, the device functions as-a shunt trip to permit tripping of the circuit breaker from a remote location.

BACKGROUND OF THE INVENTION Field of the invention Our invention relates to electric circuit breakers and more particularly to circuit breakers including auxiliary devices of the undervoltage release and shunt trip types.

Description of the prior art In accordance with the prior art, circuit breakers have been provided with undervoltage and shunt trip devices for the respective purposes of causing tripping of the breaker when an undesirable drop in voltage occurs and for enabling a breaker to be tripped from a remote location. Generally speaking, such devices comprise a solenoid having a plunger movably mounted therein wherein movement of the plunger in a given direction is utilized to cause tripping of the circuit breaker. In prior art structures, the plunger having completed its movement to cause tripping of the breaker is returned to its reset position through the action of a part of the circuit breaker contact arm or other part of the circuit breaker mechanism as the circuit breaker mechanism moves to its open position as a result of the tripping thereof.

With such an arrangement the plunger is. held in its reset position so long as the circuit breaker is in its open condition. Accordingly, the breaker must begin its movement toward closed position before the plunger of the auxiliary device can become operative to cause retripping of the breaker. Thus, irrespective of the relative position of the operating parts of the auxiliary device, the circuit breaker can always begin a closing operation. Because of the nature of commonly used circuit breaker mechanisms, this means that the contacts of the circuit breaker can temporarily close or touch before the breaker mechanism is returned to its open position by virtue of the retripping action of the auxiliary device. Also, for this same reason, this type of device cannot be used as an electrical interlock, that is, to prevent for example the closing of the circuit breaker contacts should the undesirable drop in voltage in the breaker circuit continue to exist.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an auxiliary device for tripping .an electric circuit breaker upon the occurrence of predetermined electrical conditions wherein the device after causing tripping of the breaker also prevents the beginning of a subsequent circuit breaker closing operation and thus any temporary closing or touching of the contacts of the breaker until or unless the aforesaid predetermined electrical conditions no longer exist.

It is another object of the present invention to provide an auxiliary device for tripping an electric circuit breaker upon the occurrence of predetermined electrical conditions wherein the device after causing tripping of the breaker prevents relatching of the circuit breaker mechanism which is necessary prior to re-closing of the breaker contacts, and which does so regardless of the position of the circuit breaker mechanism or contact arms until or unless the aforesaid predetermined electrical conditions no longer exist.

A still further object of the present invention is to provide an auxiliary device for tripping an electric circuit breaker which is capable of serving as an electrical interlock to prevent closing of the breaker contacts upon the presence of predetermined electrical conditions in a reference circuit.

Another object of the present invention is to provide an auxiliary device for tripping an electric circuit breaker wherein the device is reliable in operation, simple in construction, and relatively inexpensive to manufacture.

Yet another object of the present invention is to provide an auxiliary device for tripping an electric circuit breaker wherein the device is readily useable with presently existing circuit breakers without requiring any substantial modifications in the breaker.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided an electrical circuit breaker including an insulating casing having a pair of relatively movable contacts supported therein, the contacts being movable between open and closed circuit positions. Releasable means is provided to cause movement of the contacts to the open circuit position. Latch means is supported in the casing and releasably engages the releasable means. An auxiliary device, which is suitably mounted in the casing for engagement with the latch means, causes release of the releasable means from the latch means upon the occurrence of predetermined electrical conditions to thereby cause opening of the contacts. The auxiliary device includes a solenoid actuated latch member which when released by the solenoid becomes disengaged from a spring-biased tripping slide of the device whereby the tripping slide, being thus free, moves under the influence of its spring bias and strikes the aforesaid latch means of the breaker mechanism thereby causing tripping of the breaker. The circuit breaker mechanism, in moving to the open condition as a result of the tripping of the breaker, engages the tripping slide of the auxiliary device and moves it against its spring bias to reset or relatched position, where it is held by the latch member of the auxiliary device. Should the aforesaid predetermined electrical conditions continue to exist, the latch member of the auxiliary device will not hold the tripping lever of the device in the relatched position because of the action of the solenoid associated therewith, whereby the tripping slide prevents the releasable means of the breaker from being relatched. Consequently the breaker contacts remain separated since the circuit breaker mechanism must be latched before the contacts can be closed.

3 BRIEF DESCRIPTION OF THE DRAWING In the drawings: I

FIGURE 1 is a side elevational view of an electric circuit breaker incorporating the present invention with a portion of the side wall of the insulating casing being broken away for clarity of illustration, and showing the circuit breaker operating elements in the closed circuit position;

FIGURE 2 is an exploded perspective view of a portion of the circuit breaker of FIGURE 1, illustrating on an enlarged scale the cradle latch, the intermediate latch mechanism, and the auxiliary device thereof in accordance with the present invention;

FIGURE 3 is a side elevational view of the auxiliary device of the circuit breaker of FIGURE 1, comprising an undervoltage trip device, the operative parts thereof being shown in the latched condition;

FIGURE 4 is a side elevational view of a portion of the circuit breaker of FIGURE 1 illustrating the cooperation between the operative parts of the intermediate latch mechanism;

FIGURE 5 is a cross-sectional view of the auxiliary device of FIGURE 3, taken substantially on the line 5-5 of FIGURE 3; and

FIGURE 6 is a side elevational view of another embodiment of an auxiliary device in accordance with the present invention comprising a shunt trip device, the operative parts thereof being shown in the latched condition.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, and more particularly to FIGURE 1 thereof, the invention is shown embodied in a circuit breaker designated by the numeral 10 which has a generally rectangular insulating casing with a base portion 11 and a removable cover portion 12. For convenience, the construction of a single pole chamber of the circuit breaker 10 is shown and will be described in detail although it will be understood that the circuit breaker 10 generally includes three pole chambers, all substantially identical except that the center pole chamber contains the major portion of the operating mechanism.

A line terminal (not shown) is supported at one end of the base portion 11 and is electrically connected to one end of a conductive strap 13, the latter having a relatively stationary contact 14 supported at the other end thereof. A load terminal (not shown) is supported at the other end of the base portion 11 of the circuit breaker, and is electrically connected to a conventional circuit breaker trip unit 15, the latter being supported in close proximity to the load terminal.

A pivoted contact arm assembly, indicated generally by the reference numeral 16, is supported in the base portion 11 of the circuit breaker between the trip unit 15 and the stationary contact 14. The pivoted contact arm assembly 16 includes a current carrying support block 17 which is fastened by means of bolts 18 (only one shown) to the base portion 11 of the circuit breaker, and an elongated contact arm segment 19 supported on the block 17 by means of the pivot pin 20. The contact arm segment 19 carries at its free end a movable contact 21. The contact arm pivot assembly 16 also includes a U-shaped bracket member 22 which overlies the contact arm segment 19, and is, also pivotally supported on the pivot pin 20. Any suitable restraining means which will not interfere with the pivoting of the U-shaped bracket member 22 may be utilized to hold the latter on the pivot pin 20. Suitable biasing means (not shown) are provided between the bracket member 22 and the contact arm segment 19 resiliently limiting movement of the arm segment 19 toward the back of the contact arm assembly 16.

Pivotally mounted on the frame member 23 by the pivot pin 24 is the pivoted end portion 25 of the releasable member or cradle generally designated by the numeral 26. The opposite end of the releasable member 26 carries a roller 27 which is rotatably mounted thereon by means of the pin 28. The roller 27 engages the end portion 29a of the primary latch 29 of the intermediate latch mechanism, generally designated by the reference numeral 30, in a manner to be more fully described hereinafter. The. cradle 26 and the contact arm pivot assembly 16 are connected intermediate their ends by the pivot pins 31, 32 to the toggle linkage provided by the toggle links 33, 34 which are pivotally connected to each other by the knee pin 35. The toggle linkage is biased toward straightened condition by a pair of tension springs 36 (the second spring is behind the cradle 26) which are engaged by the knee pin 35 at one end and attached to the pin 37 fixedly carried by the frame member 23, at the other end.

-The fixed ends of the tension springs 36 are thus spaced toward the stationary contact 14 to the side of the line drawn between the pivot pins 31, 32 for the toggle links 33, 34 in the latched position of the cradlev 26. Thus, the springs bias the toggle links 33, 34 toward the stationary contact 14 in the latched position of the cradle 26 as shown in FIGURE 1. At the same time the springs 36 tend to rotate the cradle 26 in a counterclockwise direction (as viewed in FIGURE 1) about the pivot pin 24 to hold the roller 28 against the end portion 29a of the primary latch 29.

Referring now to FIGURE 2, the primary latch 29 of the intermediate latch mechanism 30 is pivotally mounted by means of pivot pin 38 on the supporting frame members 39 of the latch mechanism 30, while the entire mechanism 3t] is supported within the circuit breaker housing by suitable means, not shown. Primary latch 29 has a radius on the end portion 29a which has a center slightly to. the back of the pivot point of the latch 29 itself. This causes the primary latch 29 to be biased backwardly due to the breaker mechanism force being exerted on the end portion 29a of the latch 29. The primary latch bias force is then transmitted to an intermediate latch 40 which further reduces the force components, so that the final tripping force required on the tripping latch lever 41 is very low compared to the initial breaker force. The tripping latch lever 41 is spring biased upwardly by the latch reset spring 42. A similar latch reset spring 43 interconnects the intermediate latch 40 and the primary latch 29. As best seen in FIGURE 2, the latch lever 41 is suitably provided with a slot 41a which engages the hook portion 40a of the intermediate latch 40 when the latter are in the latched position.

As seen in FIGURE 1, the trip unit 15 is supported within the base portion 11 of the circuit breaker closely adjacent the contact arm pivot assembly 1 6 and the intermediate latch mechanism 30, and is electrically connected to the current carrying support block 17 of the contact arm pivot assembly 16 by means of the connector 44 which fixedly secures the terminal 45 of the trip unit 15 to the block 17. In order to complete the current carrying path through the circuit breaker 10, the trip unit 15 is provided with another terminal (not shown) which is connected in the conventional manner to the load terminal (not shown) of the circuit breaker, referred to earlier.

Housed in the trip unit 15 is a conventional thermal sensitive device (not shown) and a conventional magnetic sensitive device (also not shown). Upon the occurrence of overload conditions of current flow through the circuit breaker, one or the other of these devices operates automatically to cause the trip bar 46 to move in a counterclockwise direction as viewed in FIGURE 1. During the course of this counterclockwise or downwardly movement, the trip bar 46 engages the calibrating screw 47 supported on the tripping latch lever 41 of the intermediate latch mechanism 30 causing the latch lever 41 to also pivot downwardly, about pivot pin 48 and against the bias of latch reset spring 42. Thistripping movement of the latch lever 41 is transmitted to the primary latch 29 by means of the intermediate latch 40 whereby movement of the primary latch 29 releases the cradle 26 of the circuit breaker to thereby cause opening of the contacts 14 and 21 in the conventional manner.

For the purpose of causing actuation of the tripping latch lever 41 upon the occurrence of predetermined low voltage conditions in the circuit, the circuit breaker 10 is provided with an undervoltage trip auxiliary device, generally designated by the reference numeral 49, which is mounted on a frame side of the center pole of the breaker by means of screws (not shown). As best seen in FIGURES 2 and 3, the undervoltage trip device 49 ineludes an energizing coil 50 which is provided with leads 51 for connection to a suitable power source and which is fixedly mounted on frame member 52 by means of a pair of screws (not shown). Plunger 53 which extends outwardly of the energizing coil 50 is supported in the coil 50 for movement relative thereto, and has one end attached to the latch 54 by means of pin 55 whereby movement of the plunger 53 is imparted to the latch 54. As viewed in FIGURE 2, the latch 54 is biased in a downwardly direction by spring 56 which has one end attached to the latch 54 and the other to the screw 57 which may be rotated in order to adjust the amount of spring force being applied to the latch 54 by the spring 56. Screw 57 is rotatably mounted in support bracket 58 which is fixedly secured to the frame member 52 by suitable means such as by a pair of rivets 59.

The undervoltage trip device 49 further includes a slide 60 which is slidably supported on the frame member 55 in spaced relation thereto by means of guide pins 61, 62, 63, the pin 61 being received in slot 60a suitably provided in the slide 60, As best seen in FIGURE 3, the slide 60 is provided with a roll pin 64 which extends outwardly in juxtaposed relation to the latch 54 so as to be engageable by the notched portion 54a of the latch 54 whereby the slide 60 may be held in latched position against the bias of spring 65 when the coil 50 is energized. Spring 65 which biases the slide 60 in a downwardly direction as viewed in FIGURE 2, has one end fixed to the stud 66 and the other fixed to the bracket 58. Also mounted on the slide 60 is a spring 67 which has one end fixedly secured thereto by means of rivet 68 while the other end 67a of the spring 67 which is freely movable extends outwardly through the slot 60b suitably provided in slot 60 and into the path of movement of the latch 54 for a purpose to be more fully described hereinafter.

Referring now to FIGURES 2, 3, and 4, when the voltage in the electrical circuit to which the leads 51 are connected drops below a predetermined level, the coil 50 becomes deenergized. The latch 54 will thus move in a downwardly direction to the position illustrated in phantom lines in FIGURE 3 because the spring force being applied thereto by spring 56 is now of sufficient strength to overcome the upward pull being applied to latch 54 through plunger 53 by the coil 51 The downward movement of the latch 54 disengages the notched portion 54a of latch 54 from the roll pin 64- thereby allowing the slide 60' to move downwardly as viewed in phantom in FIGURE 3 under the influence of the spring force being applied thereto by spring 65. In doing so, projection 60c on the slide 60 strikes the tripping latch lever 41 moving it downwardly to the position shown in phantom lines in FIGURE 4 to thereby cause the breaker to trip. This occurs by virtue of the fact that the downward movement of latch lever 41 releases the intermediate latch 40 and thereby causes the primary latch 29 to release the cradle 26 whereby the contacts 14 and 21 are opened. It is thus seen that the undervoltage trip device 49 causes the contacts 14 and 21 to open in a manner similar to that previously described in connection with the automatic tripping of the circuit breaker resulting from the sensing of overload currents by the current sensitive devices housed in the trip unit 15.

When the breaker trips, the cradle 26 pivots about pivot pin 24 in an upwardly direction as viewed in FIGURES 1 and 2 during which movement the cradle pin 68 engages the end portion 60d of slide 60 to thereby cause the slide 60 to also move in an upwardly direction against the bias of spring 65. While the slide 60 moves upwardly, the freely movable end 67a of spring 67 engages the latch 54 causing the latter to pivot in an upwardly direction whereby the notched portion 54a of the latch 54 is positioned so as to reengage the roll pin 64 carried by the slide 60. When the breaker is reset in the conventional manner, the cradle 26- is moved in a downwardly direction back to the latched position where it is held by the primary latch 29. The slide 60, however, does not follow the cradle 26 during the latters downward movement since the latch 54 by virtue of the engagement of the notched portion 54a thereof with roll pin 64 holds the slide 60 in its upper position as viewed in FIGURES 2 and 3. With the breaker reset, the contacts 14 and 21 may then be reclosed by operation of the handle 69 in the manner described and claimed in the copending application of C. L. Jencks and G. W. Kiesel, Ser. No. 597,946 filed Nov. 30, 1966, and assigned to the same assignee as the present application.

If however when the breaker is reset the coil 50 is not energized, then the latch 54 because of the force being applied thereto by spring '56 will pivot downwardly as viewed in FIGURES 2 and 3 and will not hold the roll pin 64. The slide 60 will therefore follow along with the cradle pin 68 in a downwardly direction such that the engagement of the projection 600 of slide 60 with the tripping latch lever 41 moves the latter downwardly preventing the cradle 26 from becoming latched by the engagement therewith with the primary latch 29. Consequently the springs 36 of the breaker mechanism will hold the contacts 14 and 21 in an open condition. It is therefore seen that inasmuch as the breaker cannot be reset if the coil 50 is deenergized and inasmuch as the breaker must be reset before the contacts 14 and 21 can be reclosed, the possibility, so commonly found to exist with prior art devices of the contacts either touching or slightly closing before operation of the undervoltage device causes in essence the retripping of the breaker is completely eliminated in accordance with the present invention by the undervoltage device 49. Furthermore by virtue of the elimination of the aforesaid possibility of the contacts touching or slightly closing, the undervolt-age device 49 of the present invention may be used as an electrical interlock to prevent reclosing of the contacts when the voltage in the circuit to which the leads 51 are connected is below a predetermined level and the coil 50 is therefore deenergized.

Referring now to FIGURE 6, there is illustrated another embodiment, generally designated by the reference numeral 70, of the auxiliary device of FIGURES 2, 3, 4, and 5, which has been modified so as to function as a shunt trip device rather than as an undervoltage trip device whereby through its use the breaker can be caused to trip by a predetermined decrease in voltage such as may occur accidentally or intentionally for purposes of remote control in response to the operation of some remote device such as a switch or relay. Elements common to the undervoltage trip illustrated in FIGURE 3 and the shunt trip illustrated in FIGURE 6 are identified by use of the same reference numerals.

With continued reference to FIGURE 6, the slide 60 of the shunt trip device 70 is normally retained in latched position by means of the engagement of roll pin 64 carried by the slide 60 and the notched portion 54a of latch 54. In the shunt trip device 70, the latch 54 is held in slide engaging position by the upwardly directed spring force applied thereto by spring 71 rather than by the pull of an energized coil as in the case of the undervoltage trip device 49 of FIGURE 3. The spring 71 has one end suitably fixed to the latch 54 and the other affixed to pin 63. The coil 72 of shunt trip device 70 comprises a pushtype solenoid having a plunger 73 movably supported therein and having one end thereof extending outwardly of the coil 72 for engagement with the latch 54 by means of pin 74 whereby movement of the plunger 73 may be imparted to the latch 54. By means of electrical power supplied to the coil 72 through leads 51 which are connected to a suitable power source, the plunger 73 of coil 72 may under predetermined conditions be caused to extend itself, i.e., move outwardly of the coil 72 which movement of the plunger 73 is imparted to the latch 54 causing the latter to pivot in a downwardly direction as viewed in FIGURE 6. The downward movement of the latch 54 results in a disengagement of the roll pin 64 from the notched portion 54a of latch 54 thereby freeing the slide 60 for movement in a downwardly direction also as viewed with reference to FIGURE 6.

From this point onward the operation of the shunt trip device 70' and the undervoltage trip device 49 are identical. Thus, in both devices during the downward movement of slide 60, the projection 60c thereof engages the tripping latch lever 41 of the intermediate latch mechanism 30 causing the latch lever 41 to also move downwardly whereby roller 27 of the cradle 26 becomes freed from engagement with the primary latch 29 in the manner previously set forth with respect to the operation of the undervoltage trip device 49 with the result that the con tacts 14 and 21 are caused to open.

Similarly, both devices are reset in the same manner. That is, during the upward movement of cradle 26 about pivot pin 24 as viewed with reference to FIGURES 1 and 2, the cradle pin 68 carried by cradle 26 engages the end portion 60d of slide 60, of shunt trip device 70 for example, causing the slide 60 to also move upwardly. When roll pin 64 once again becomes engaged with the notched portion 54a of latch 54, slide 60 of shunt trip device 70 will be held in its upward position by virtue of the force being applied thereto by spring 71 as previously described. However, should conditions be such in the electrical circuit to which leads '51 of shunt trip device 7 are connected such that the plunger 73 remains extended, the latch 54 which is connected thereto by pin 74 will remain in its downward position whereby the notched portion 54a thereof will not engage roll pin 64. Thus, when an attempt is made to reset the cradle 26 in the manner previously described in connection with the operation of the undervoltage trip device 49, the slide 60 will follow along with the cradle pin 68 such that the engagement of the projection 600 of slide 60 with the tripping latch lever 41 prevents the cradle 26 from becoming latched by the engagement therewith with the primary latch 29.

While the invention has been shown in two embodiments, it will be apparent that many other modifications thereof may be made, and We therefore intend by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising:

(a) an insulating casing;

(b) a pair of relatively movable contacts supported in said casing, said contacts being movable between open and closed circuit positions;

(c) an operating mechanism supported in said casing, said operating mechanism including a cradle member releasable to cause movement of said contacts to said open circuit position;

((1) latch means supported in said casing, said latch means releasably engaging said cradle member;

(e) an auxiliary device mounted in said casing for engagement with said latch means;

(f) said auxiliary device including a latch member, mounted for movement between a first position and a second position, means responsive to the occurrence of predetermined circuit conditions to cause movement of said latch member from said first position to said second position, a movably mounted slide member, means releasably holding said slide member in engagement with said latch member when said latch member is in said first position, and spring means operative when said latch member is in said second position to cause said slide member to move into engagement with said latch means to release said cradle member and thereby cause tripping of said circuit breaker and opening of said contacts;

(g) said operating mechanism further including reset means operatively only upon the tripping of said circuit breakers, said reset means when operative engaging said slide member to cause movement of said slide member into position for re-engagement with said latch member of said auxiliary device;

(h) means for returning said cradle member to the relatched condition wherein said cradle member is again releasably engaged by said latch means; and

(i) said releasably holding means of said auxiliary device upon the continued existence of said predetermined circuit conditions being incapable of bolding said slide member in engagement with said latch member of said auxiliary device as said cradle member is returning to said relatched condition whereby said slide member is again moved into engagement with said latch means by said spring means thereby preventing relatching of said cradle member and movement of said contacts to said closed circuit position.

2. An electric circuit breaker comprising:

(a) an insulated casing;

(b) a pair of relatively movable contacts supported in said casing, said contacts being movable between open and closed circuit positions;

(0) means including a cradle member releasable to cause movement of said contacts to said open circuit position;

(d) latch means supported in said casing, said latch means releasably engaging said cradle member;

(e) an auxiliary device mounted in said casing for engagement with said latch means;

(f) said auxiliary device including a latch member mounted for movement between a first position and a second position, means responsive to the occurrence of predetermined circuit conditions to cause movement of said latch member from said first position to said second position, a movably mounted slide member, means releasably holding said slide member in engagement with said latch member when said latch member is in said first position, and means operative when said latch member is in said second position to cause said slide member to move into engagement with said latch means to release said cradle member and thereby cause tripping of said circuit breaker and opening of said contacts;

(g) resetting means carried by said cradle member, said resetting means engaging said slide member after release of said cradle member by said latch means to cause movement of said slide member into position for re-engagement with said latch member of said auxiliary device;

(h) means for returning said cradle member to the relatched condition wherein said cradle member is again releasably engaged by said latch means; and

(i) said releasably holding means of said auxiliary device upon the absence of said predetermined circuit conditions releasably holding said slide member in engagement with said latch member of said auxiliary device as said cradle member is returned to said relatched condition.

3. An electric circuit breaker as defined in claim 2 75 wherein:

(a) said auxiliary device comprises an undervoltage trip release device;

(b) said means responsive to the occurrence of predetermined circuit conditions includes an energizing coil normally holding said latch member in said first position, means connecting said coil to said latch member, and a spring operative upon the occurrence of said predetermined circuit conditions to cause movement of said latch member from said first position to said second position; and

(c) said resetting means carried by said cradle member comprises a pin member fixedly secured to said cradle member adjacent one end thereof.

4. An electric circuit breaker as defined in claim 2 wherein:

(a) said auxiliary device comprises a shunt trip device;

(b) said means responsive to the occurrence of predetermined circuit conditions includes a spring normally holding said latch member in said first position, an energizing coil operative upon the occurrence of said predetermined circuit conditions to cause movement of said latch member from said first position to said second position, and means connecting said coil to said latch member; and

(c) said resetting means carried by said cradle member comprises a pin member fixedly secured to said cradle member adjacent one end thereof.

5. An electric circuit breaker comprising:

(a) an insulated casing;

(b) a pair of relatively movable contacts supported in said casing, said contacts being movable between open and closed circuit positions;

(c) means including a cradle member releasable to cause movement of said contacts to said open circuit position;

(d) latch means supported in said casing, said latch means releasably engaging said cradle member;

(e) an auxiliary device mounted in said casing for engagement with said latch means;

(f) said auxiliary device including a latch member mounted for movement between a first position and a second position, means responsive to the occurrence of predetermined circuit conditions to cause movement of said latch member from said first position to said second position, a movably mounted member, means releasably holding said movably mounted member in engagement with said latch member when said latch member is in said first position, and spring means operative when said latch member is in said second position to cause said slide member to move into engagement with said latch means to release said cradle member and thereby cause tripping of said circuit breaker and opening of said contacts;

(g) resetting means carried by said cradle member, said resetting means engaging said movably mounted member after release of said cradle member by said latch means to cause movement of said slide member into position for re-engagement with said latch member of said auxiliary device;

(h) means for returning said cradle member to the relatched condition wherein said cradle member is again releasably engaged by said latch means; and

(i) said releasable holding means of said auxiliary device upon the continued existence of said predetermined circuit conditions being incapable of holding said movably mounted member in engagement with said latch member of said auxiliary device as said cradle member is returning to said relatched condition whereby said movably mounted member is again moved into engagement with said latch means by said spring means thereby preventing relatching of said cradle member and movement of said contacts to said closed circuit position.

6. An electric circuit breaker as defined in claim 5 wherein:

(a) said auxiliary device comprises an undervoltage trip release device;

(b) said means responsive to the occurrence of predetermined circuit conditions includes an energizing coil normally holding said latch member in said first position, means connecting said coil to said latch member, and a spring operative upon the occurrence of said predetermined circuit conditions to cause movement of said latch member from said first position to said second position; and

(c) said resetting means carried by said cradle member comprises a pin member fixedly secured to said cradle member adjacent one end thereof.

7. An electric circuit breaker as defined in claim 5 wherein:

(a) said auxiliary device comprises a shunt trip device;

(b) said means responsive to the occurrence of predetermined circuit conditions includes a spring normally holding said latch member in said first position, an energizing coil operative upon the occurrence of said predetermined circuit conditions to cause movement of said latch member from said first position to said second position, and means connecting said coil to said latch member; and

(c) said resetting means carried by said cradle member 45 comprises a pin member fixedly secured to said cradle member adjacent one end thereof.

References Cited UNITED STATES PATENTS 2,566,866 9/1951 Yarrick 335-20 3,175,064 3/1965 Myers 33520 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner.

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