US3548358A - Electric circuit breaker with bimetallic strip protective means - Google Patents

Description

K. w. KLEIN Dec. 15, 1970 ELECTRIC CIRCUIT BREAKER WITH BIMET'ALLIC STRIP PROTECTIVE MEANS 2 Sheets-Sheet 1 & iinil lim lm w w 7 W i u Filed May 19, 1969 m 88 BQM WT N M w M 1 N m f V W W r lav W De.' 15,1 970. W LEW 3 59mm ELECTRI [C CIRCUIT BREAKER WITH BIMETALLIC STRIP PROTECTIVE- MEANS Filed May 19, 1969 2 Sheets-Sheet ATTORNEY United States Patent O 3,548,358 ELECTRIC CIRCUIT BREAKER WITH BIMETALLIC STRIP PROTECTIVE MEANS Keith W. Klein, Simsbury, Conn., assignor to General Electric Company, a corporation of New York Filed May 19, 1969, Ser. No. 825,610 Int. Cl. HOlh 71/16 US. Cl. 337-83 9 Claims ABSTRACT OF THE DISCLOSURE A manually operated on/off handle of a circuit breaker is provided with a pair of depending lugs adapted to contact the trip bar during the resetting operation and assure positive opening of the trip mechanisms electromagnetic shunting circuit.

BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to electrical circuit breakers and the like. In particular it is directed to a new and improved circuit breaker or similar circuit control device having a current-responsive trip mechanism for opening the circuit upon the occurrence of a predetermined current condition.

Heretofore circuit breakers of the type described have included both thermal and electromagnetic trip mechanisms either alone or in combination. The electromagnetic trip portion of such combined structures generally includes a pair of shunting contacts which close to bypass a portion of the high overload currents and thereby protect the thermally responsive trip element from burn-out on short circuit. Despite the fact the shunting contacts are made from high refractory material, a short circuit can cause them to lightly weld and thus prevent resetting of the circuit breaker.

Accordingly an object of the present invention is to provide an electrical control device of the type described having a new and improved mechanism for assuring positive and automatic opening of the shunting circuit as the circuit breaker is reset even if the shunting contacts are lightly welded.

Another object of the present invention is to provide a new and improved circuit breaker having a reset mechanism operatively associated with a shunting trip mechanism, the reset mechanism including means which operate automatically during the relatching of the trip mechanism to assure opening of the shunting circuit breaker prior to complete resetting of the circuit breaker.

A further object of the present invention is to provide a new and improved circuit breaker constructed so that the aforementioned objects are accomplished without the necessity of additional manipulative operations. Included in this object is the provision for a circuit breaker having a handle movable from the trip position to the reset position for resetting the breaker, the movement of the handle into the reset position being effective to break any weld between shunting contacts and reset the trip mechanism of the circuit breaker.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

These and related objects are accomplished in accordance with the present invention by providing a new and improved circuit breaker having a handle movable between on, trip and reset positions for opening and closing a circuit across the breaker, current responsive trip release means including shunting contacts movable into a closed position upon the occurrence of an overload current condition and a shunt weld breaking member as- ICC sociated with the handle and operable upon movement of the handle between the trip and reset positions to positively open the shunting contacts when the contacts are welded in the closed position by an overload current condition.

A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and the accompanying drawings which set forth certain illustrative embodiments and are indicative of the various Ways in which the principle of the invention is employed.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a plan view of a multi-pole circuit breaker incorporating the features of the present invention, the handle of the circuit breaker being located in its on position;

FIG. 2 is a side elevational view of the circuit breaker of FIG. 1, partially broken away and partially in section, illustrating the relative positioning of the trip and reset mechanisms during normal closed circuit operation;

FIG. 3 is an exploded isometric view of the trip and reset mechanisms of FIG. 2 including a fragmentary portion of the circuit breaker handle;

FIG. 4 is an elevational view of the trip and reset mechanisms of the circuit breaker of FIG. 2 after the occurrence of an overload current condition sufiicient to activate the electromagnetic trip structure, the handle being shown in its trip position; and

FIG. 5 is an elevational view similar to FIG. 4 showing the relative positioning of the trip and reset mechanisms during the resetting operation immediately prior to separation of shunt contacts welded in the closed position on short circuit.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings in greater detail wherein like reference numerals indicate like parts throughout the several figures, there is shown in FIGS. 1 and 2 a two pole electric circuit breaker having an insulating casing comprised of a generally rectangular base portion 10 and an enclosing cover portion 12. Protruding through the cover 12 is a manually operated handle 14 operatively connected for closing both poles across the circuit breaker to provide an electrical connection between each load terminal 16 located at one end of the breaker and its respective line terminal 18 positioned at the breakers opposite end, the connection being effected through separate trip release mechanisms, generally designated 22 and separate main circuit contacts (not shown). A single resettable trip mechanism, generally designated 24, operatively controls both poles so that an overload condition within one circuit will open both circuits controlled by the breaker.

As shown, a longitudinal slot 26 in the top of cover portion 12 is offset transversely from the center of the casing and positioned above one of the poles of the breaker. The pivotable handle 14 mounted within the casing includes a protruding button 28 extending through the top slot 26 to facilitate manual control thereof and movement of the handle into its on position with the button 28 at one end of the slot and its oif/reset position with the button at the opposite end thereof. The movement of the handle into and out of these positions controls the operation of the circuit breakers operating mechanism which, in turn, controls the movement of a releasable trip member 32 between its released trip position illustrated in FIG. 4 and its latched position illustrated in FIG. 2. The trip member 32 is held in its latched position by other members of the trip mechanism 24 which includes a generally U-shaped trip latch 34 and a trip bar 36, each best shown in FIG. 3.

The latch 34 and bar 36 are each mounted within the casing for limited pivotal movement between their latched and released positions. The trip bar 36 extending transversely across both poles of the circuit breaker includes a latch-l1olding projection 38 which contacts an edge of the latchs crossbar portion 42 and holds the latch in its latched position shown in FIG. 2. The trip bar 36 is provided with a return spring 44 which biases the bar in a counterclockwise direction as viewed in FIG. 2 to assure firm holding engagement between the projection 38 and the latch 34. However, upon clockwise movement of the trip bar against the bias of return spring 44, the projection 38 moves away from the latchs crossbar portion 42 and permits the latch to move out of its latched position under the clockwise driving force of the releasable trip member 32. Movement of the trip member out of its latched position causes the operating mechanism to open the main circuit contacts of every circuit controlled by the circuit breaker and simultaneously move the handle 14 to the trip position shown in FIG. 4.

The releasable trip member 32 is provided with a slight- 1y arcuate front edge 46 which in the tripped position of the breaker contacts the crossbar portion 42 of the latch and moves it toward the latchs released position where it abuts a raised boss 48 carried by the projection 38 of the trip bar and recessed slightly from the forwardmost end thereof. The cooperative engagement between the boss 48 and the latch holds the trip bar in its tripped or released position against the bias of its return spring 44. However, movement of the handle 14 from the trip position shown in FIG. 4 rearwardly toward the reset position causes the operating mechanism to move the releasable trip member 32 in a counterclockwise direction as viewed in FIG. 4 until the releasable trip member clears the crossbar portion 42 of the latch and permits the drive spring 44 to return the trip bar 36 to the position shown in FIG. 2. The latch in turn slides off boss 48 and is held by the projection 38 in its latched position where it latches the releasable trip member 32.

As mentioned hereinbefore, an overload current condition within either circuit controlled by the circuit breaker will activate the automatic trip release mechanism 22 associated with that circuit causing clockwise movement of the trip bar 36 and automatic opening of all circuits controlled by the circuit breaker. Thus the load terminal 16 for each pole of the circuit breaker is provided with a separate trip release mechanism 22 incorporating both a thermally responsive current-carrying trip device and an electromagnetic trip structure operative at high current values to protect the thermally responsive bimetal device against burn-out. In the particular embodiment illustrated, the thermally responsive trip device consists essentially of a bimetal strip 52 of generally L-shaped configuration, having a flat base portion 54 firmly secured to the base portion of the casing. A load terminal strap 56 is directly connected to the top free end 58 of the bimetal strip by means of a flexible conductor or braid 62 while a connecting strap 64 electrically connected to the main circuit contacts is in intimate surface engagement with the strips base portion 54. Accordingly, the main current path through each pole of the circuit breaker when the main contacts are in their closed circuit position is from the load terminal strap 56 through the flexible conductor 62 to the bimetallic strip 52, through the strip 52 and along the connecting strap 64 to the main circuit contacts connected to the line terminal 18.

The top free end 58 of the bimetallic strip 52 is provided with a calibrated screw 66 extending outwardly therefrom toward the trip bar 36. Upon the occurrence of an overload current of low value the bimetallic strip will heat causing deflection thereof toward the trip bar. Upon sufficient deflection, the calibrated screw 66 will engage and drive the trip bar 36 clockwise against the bias of its return spring 44 effecting release of the releasable trip member 32 by the latch 34.

As mentioned hereinbefore the trip release mechanism 22 for each pole of the circuit breaker also includes an electromagnetic trip structure. In the embodiment illustrated, the trip structure takes the form of a generally U-shaped field magnet 72 spaced from three sides of the bimetallic strip 52 passing therethrough. An integral support member 74 for the magnet is fixedly secured to the base of the casing and held in intimate surface contact with the base portion 54 of the bimetallic strip by suitable means such as the bolt 76. A flat magnetically responsive shunting plate 78 is mounted for pivotal rotation within the casing by means of a pair of integral side arms 82 extending outwardly therefrom. The plate 78 is positioned within the casing juxtaposed the open end of the Ushaped magnet 72 for attraction thereto upon the occurrence of overload currents of high value. As illustrated, the plate 78 mounts a shunt contact 84 for contact with a fixed shunt contact 86 carried by the magnet upon attraction of the plate to the magnet. The plate 78 is electrically connected to the top free end 58 of the bimetallic strip by means of a flexible connector or braid 88 so that upon the occurrence of an overload current of high value a closed shunt circuit is provided between the terminal strap 56 and connecting strap 64 through the magnet 72 thereby causing a portion of the overload current to bypass the bimetallic strip 52 and prevent burn-out thereof.

The plate 78 is further provided with an upstanding armature 92 extending from a point above the side arms 82 at an angle to the contact carrying portion of the plate, as best seen in FIGS. 2, 4 and 5. As will be appreciated, clockwise rotation of the shunting plate as viewed in FIG. 2 under the influence of magnet 72 will cause armature 92 to move into engagement with the trip bar 36, driving it against the bias of return spring 44 to effect release of the trip member 32 by the latch 34. A coiled drive spring 94 adapted to bias the shunting plate in a counterclockwise direction against the attractive force of the magnet is mounted on one side arm 82 for return of the shunting plate to its rest position shown in FIG. 2 after the main circuit of the breaker has been opened.

As mentioned hereinbefore, sometimes the shunt contacts 84, 86 are welded in a closed position on short circuit duty causing the armature 92 to continuously hold the trip bar 36 in the released position illustrated in FIG. 4 preventing reset of the circuit breaker. In accordance with the present invention the the reset mechanism includes shunt opening means capable of breaking the weld between the shunt contacts without the necessity of additional manipulative operations. In the preferred embodiment this is accomplished by providing the handle 14 with a pair of rigid, integral lugs or projections 96 extending downwardly toward the interior of the breaker. The projections 96 are positioned adjacent one end of the handle so that upon movement of the handle from the trip position toward the reset position the projections come into driving contact with the trip bar 36. It is an advantageous feature of the present invention that the location of the projections provides for the full return of the releasable trip member 32 to its latching position, as illustrated in FIG. 5, before the projections 96 come into contact with the trip bar. In this way driving engagement is caused between the handle projections and the trip bar upon continued movement of the handle toward the reset position. This in turn generates a sufficient force on the armature 92 to break the weld holding the shunt contacts closed and facilitates movement of the latch 34 into its latching position. As will be appreciated, immediately upon breaking the weld the shunting plate drive spring 94 returns the shunting plate to its rest position shown in FIG. 2 and the return spring 44 assists in moving the trip bar and latch into the latched reset position of FIG. 2. Thus, the construction of the present invention provides a positive means for assuring movement of the shunt contacts out of their closed position and resetting of the circuit breaker without requiring any additional manipulative step on the part of the operator and without subjecting the casing to potential damage from the striking thereof.

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.

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

1. An electric control. device comprising (a) a handle movable between reset, on and trip positions for closing and opening a circuit across the device,

(b) a releasable trip member movable into a latched position upon movement of the handle into its reset position and effective upon release from its latched position to cause said handle to assume the trip position,

(c) current-responsive trip release means controlling the release of said releasable trip member and including shunting contacts movable into a closed position upon the occurrence of an overload current condition of predetermined value within said circuit, and

(d) shunt opening means associated with said handle for movement upon movement of said handle between the trip and reset positions and operable on said release means to positively open the shunting contacts when said contacts are welded in the closed position by said overload current condition.

2. The control device of claim 1 wherein the trip release means includes an armature movable into and out of a rest position in response to said overload current condition to release said releasable trip member, said armature preventing latching of said trip member while said shunting contacts are in the closed position.

3. The control device of claim 2 wherein said shunt opening means is operative in synchronism with said handle upon movement thereof into the resetposition for driving said armature toward the rest position and effect opening of said shunting contacts.

4. The control device of claim 1 wherein the trip release means includes a thermally responsive member electrically connected within said circuit, said shunting contacts being connected for bypassing said thermally responsive member upon movement thereof into the closed position.

5. The circuit breaker of claim 1 wherein the trip release means includes an actuator movable between rest and trip positions in response to said overload current condition, said actuator mounting one of said shunting contacts and being moved to its trip position upon closing of said shunting contacts, said shunt opening means being operable to exert a driving force on said actuator for release thereof from its trip position.

6. The electric control device of claim 1 wherein the shunt opening means includes a drive member carried by the handle for applying a breaking force on the weld holding the shunting contacts in the closed position.

7. The electric control device of claim 1 including latching means for releasably latching said trip member and wherein the shunt opening means is operative to drive the latching means into a latching position as the contacts are opened and after movement of the trip members into a latchable position.

8. The electric control device of claim 1 wherein the current responsive trip release means includes an electromagnetic trip assembly including a stationary magnet member carrying a first shunt contact and a movable magnet member carrying a second shunt contact, said movable magnet member being provided with an armature operative to release said releasable trip member upon closing of said shunt contacts under overload current conditions within said circuit, said shunt opening means drivingly acting on said armature to cause said positive opening of the shunting contacts.

9. The electric control device of claim 1 including (a) an insulating casing,

(b) latching means for releasably latching said releasable trip member,

(c) the current responsive trip release means including a bimetal strip and an electromagnet, said strip having one end secured to said casing and an opposite free end operative on said latching means' to release the trip member, said electromagnet including a first magnet member carrying a stationary shunt contact and a second magnet member carrying a movable shunt contact, said second magnet member being provided with an armature operative on said latching means to cause release of said releasable trip member, said electromagnet providing a bypass for said strip upon closing of said shunt contacts under overload current conditions within said circuit, said armature being effective to prevent said latching means from latching said releasable trip member when said shunting contacts are welded in the closed position by said overload current conditions, said handle driving said shunt opening means against said armature upon movement from said trip position to said reset position to cause positive opening of said shunting contacts.

References Cited UNITED STATES PATENTS 2,308,401 1/ 1943 Taylor 337-77 2,426,880 9/ 1947 Jackson 337-48 2,849,581 8/1958 Bingenheimer 200153.7 3,104,297 9/1963 Powell 33783 3,211,867 10/1965 Heft 200l44 BERNARD A. GILHEANY, Primary Examiner H. BROOME, Assistant Examiner U.S. Cl. X.R.

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