GB2286486A - Circuit breaker - Google Patents

Abstract

A circuit breaker comprises first and second breaker contacts (31, 32) disposed in a main current path extending between a line terminal (20a) and a load terminal (20b). An electromagnetic release device is provided to forcibly disengage the second contact (32) from the first contact (31) upon detection of an excess current flowing through the main current path. The release device comprises a coil (51) inserted in the main current path and a plunger magnetically connected to the coil through a yoke which is of a generally U-shaped configuration having a base member (52c) and a pair of side members (52a, 52b). A pair of opposed first and second arc runners (71, 52c) are disposed to guide an arc, which develops between the breaker contacts upon separation thereof, in a direction away from the breaker contacts. The first arc runner (71) is electrically connected to the first contact (31) and extends away therefrom to give an extension (71c), while the second arc runner (52c) is defined by the base member (52c) of the yoke. The yoke is electrically connected to the second contact (32) at the side member (52a) adjacent to the second contact (32). The arc runners are confined within a space between opposed side walls of the circuit breaker housing 10, the width of the space increasing towards the advancing direction of the arc. <IMAGE>

Description

CIRCUIT BREAKER This invention concerns a circuit breaker in which the breaker contacts are forcibly opened upon seeing an excessive electrical current flowing in a main electrical path in which the breaker contacts are inserted.

Among prior circuit breakers of this type are some in which, in order to suppress arcs formed when the breaker contacts are forcibly opened due to excessive current flow in the main electrical path in which the breaker contacts are inserted, arc runners are electrically connected to the two contacts that made up the breaker contacts (either a movable contact and a fixed contact, or a pair of movable contacts).

Arcs generated by the opening of the breaker contacts are made to travel along the two arc runners, the arcs being guided so as to travel away from the breaker contacts to an arc suppression device. The coil of an electromagnetic release device is inserted in the main electrical path, the configuration being such that if excessive current flows in the coil, a plunger situated within the coil moves by magnetic force to forcibly open the breaker contacts. Hence, a switching device is provided for the purpose of holding stored spring force to open the breaker contacts.

The configuration is such that when the plunger of the electromagnetic release device moves, the spring force accumulated in the switching device is released, thereby opening the breaker contacts. Also provided in the electromagnetic release device, for more efficient action of the magnetic force acting on the plunger in the coil, is a yoke having a pair of side members opposite the axial end surfaces of the coil, and a base member connected to the two side members on the outside of the coil.

In circuit breakers having the above conventional configuration, the electromagnetic release device and arc runners are installed separately and causes a problem with a high parts count. The present invention proposes to solve the above problem by providing a circuit breaker with a reduced parts count.

The circuit breaker of the present invention has breaker contacts connected in a main electrical path between a line terminal and load terminal, the breaker contacts being composed of a first contact and a second contact The breaker includes an electromagnetic release device which, upon detection of an excess current flowing in the main electrical path, disengages second contact forcibly from first contact. The release device has a coil inserted in the main electrical path, and a plunger inserted in coil.

Plunger is caused to move in one direction by the magnetic force created by the coil when excess current flows in the coil, and breaker contacts and are then opened by the motion of the plunger. The plunger is magnetically coupled to the coil through a yoke of a generally U-shaped configuration with a base member and side members located at opposite ends of the base member.

Also provided are a pair of arc runners that cause arcs generated between first and second contacts upon separation of the breaker contacts to travel in a direction away from the contacts due to the magnetic force caused by the magnetic field generated along with the arc current, first arc runner being electrically connected to the first contact and having an extension extending in a direction away therefrom, and second arc runner being electrically connected to the second contact and extending away therefrom. The characterizing feature of the present invention is that the yoke is electrically connected to the second contact at the side member adjacent to the breaker contacts, and base member of the yoke is placed in opposing relation to extension of one of the arc runners, and base member itself defines the second arc runner. With this configuration, when one end of the arc travels to the middle part of the yoke, the arc current can be caused to flow in mutually opposing directions in arc runner and the base member of yoke, and electromagnetic force can be caused to act upon the arc such that the arc will run between the arc runner and base member of yoke, going away from the breaker contacts. Hence, the base member of yoke, installed in the electromagnetic release device, functions as an arc runner and performs double duty so that a pair of arc runners is not installed as required in the prior circuit breaker. Consequently, there is no need for a pair of arc runners, and the parts count, as compared to the prior circuit breaker, is reduced.

Further, coil is wound around a coil tube of electrically insulating material, and an electrically insulating flange is provided at one axial end of the coil tube, the flange being placed between coil and one side member which is remote from the breaker contact than the other side member. This configuration ensures insulation between the side member and coil, and provides positive prevention against arcs being driven in a direction opposite to the desired direction by the emergence of a short between these parts.

In addition, the coil surrounds a core member that includes the plunger . Retainer grooves, into which the two ends of the core member are inserted, are formed in side members of the yoke. The retainer grooves open toward the circumferences of side members , and retainer prongs, and which protrude into an inner surface of a breaker housing are inserted into the retainer grooves. Both ends of the core member are clamped between the inner peripheries of the retainer grooves. Having the retainer groove open so as to face the circumferences of the side members in this manner makes it easy to secure the core member to yoke. Moreover, since inserting the retainer prongs into the retainer grooves fixes the yoke in position on the housing, it is easy to secure the core member and the yoke in their proper positions, which simplifies the assembly process.

A narrowed section, in which the inner diameter is smaller than an intermediate section is formed at one axial end of the coil.

The diameter of the plunger has a portion that is larger than the inner diameter of the narrowed section and smaller than the inner diameter of the intermediate section, the plunger being disposed such that it is movable in the axial direction within the coil tube. A fixed core is fastened at the other axial end of coil tube, a return spring is provided between fixed core and plunger, a portion of fixed core protrudes from coil tube , one end of the coil tube is fastened to one of the side members of yoke, and fixed core is magnetically coupled at the protruding portion to the other side member of yoke. For this reason, the plunger, fixed core, and return spring can be secured inside the coil tube, which facilitates assembly of the electromagnetic release device. Moreover,- a portion of the fixed core is caused to protrude from coil tube to be magnetically coupled to the side members of yoke . This reduces the reluctance of the magnetic path formed by yoke, the fixed core, and the plunger to a relatively small value, which enables the plunger to be pulled in with strong force.

In addition, the present invention is designed to dispose both the arc runners within a space between the two side walls of the breaker housing, the width between the two side walls in the space being such that it widens toward the advancing direction of the arc. Hence, the two walls of the space that receives the arc runners are formed such that the intervening distance between them widens in the direction of the electromagnetic force acting upon the arcs, distributing arc gas pressure such that the pressure is highest in the region near the breaker contacts and decreases in the advancing direction of the arc, thereby causing the arc gas to flow in the advancing direction of the arc. In other words, the advance of the arc can be promoted by the flow of arc gas, making it possible to quickly suppress the arc. As a result, the ceramic circulator side plates separately located in the vicinity of the breaker contacts in prior circuit breakers are not required, which makes it possible to reduce parts count.

The step-shaped depressions formed in both side walls of the breaker housing create portions of the side walls that are shadowed from the arc, as seen from the breaker contacts. Thus even if the side walls are deteriorated by heat from arcing, the level of deterioration in the shadowed regions would be low. Hence, side-wall deterioration can be made relatively minor.

In addition, an incline is formed with respect to the arc runners such that the greater the distance away from the breaker contacts, the wider the distance between the arc runners. The gradual stretching of the arc and the raising ofthe arc voltage facilitates suppression of the arc. Th the rr miner as widening the distance between the side walls, a pressure distribution that causes arc gas to flow away frcm the breaker contacts is created, thus pr rsting the travel of the arc.

A number of embodiment of the invention will now be described by way of example on1ywith reference to the accanenying drawiggs in which: FIG. 1 is an exploded perspective view of one embodiment of the circuit breaker of the present invention; FIG. 2 is a perspective view showing the internal mechanism of the same circuit breaker; FIG. 3 is a perspective view of the same circuit breaker.

FIG. 4 and FIG. 5 are main-parts-only cross-section views showing the installed locations of the yoke and housing used in the same circuit breaker; FIG. 6 is a cross-section view showing the "on" state of the same circuit breaker; FIG. 7 is a cross-section view showing the "off" state of the same circuit breaker; FIG. 8 is a cross-section view showing the "tripped" state of the same circuit breaker; FIG. 9 is a horizontal cross section of the space that receives the arc runner in the same circuit breaker; and FIG. 10 is a horizontal cross section of the space that receives the arc runner in another embodiment of the circuit breaker of the present invention.

Embodiment 1 As shown in FIG. 1, the circuit breaker of the present invention has a housing 10 made of electrically insulating synthetic resin material with a line terminal 20a provided on one side of housing 10, and a load terminal 20b provided on the other side. Terminal bar 21a, which is provided with fixed contact 31 (see FIG. 2), is electrically connected to line terminal 20a. Terminal bar 21b, which secures one end of bimetal strip 61 and constitutes thermal release device 60, is electrically connected to load terminal 20b. The breaker contacts are composed of a fixed contact 31 and a movable contact 32 on a movable member 33.

Movable contact 32 makes and breaks contact with fixed contact 31 in response to the operation of switching device 40 described below.

Movable member 33 is connected through connecting wire 37 made of braided wire to one end of a coil 51 in an electromagnetic release device 50 described below. The other end of coil 51 is connected via connecting wire 38 made of braided wire to the intermediate section of bimetal 61. Accordingly, when the breaker contacts close, current flows through the main electrical path consisting up of line terminal 20a, the breaker contacts, coil 51, bimetal 61, and load terminal 20b. The bimetal 61 used here may be either the directly heated type, which bends from heat generated by itself, or the indirectly heated type, which bends when heated by a heater plate laminated to it.

As shown in FIG. 3, housing 10 is formed by fastening cover lOb to body 10a with rivets 11. That is, assembly holes 12a, 12b are bored through body 10a and cover lOb at four locations around their periphery, and cover 10b is fastened to body 10a by installing a rivet 11 in each of the assembly holes 12a, 12b. A handle insertion hole 13 is formed as a rectangular opening in the upper surface of housing 10 when cover lOb is put in place against body 10a. As shown in FIG. 2, cylindrical bearings 14 are mounted at the inside surface of body 10a and cover lOb near handle insertion hole 13. The respective ends of handle shaft 42, on which a handle 41 pivots, are inserted into the bearing holes in the centers of bearings 14. Operation member 41a provided on handle 41 is inserted through handle insertion hole 13 such that it protrudes from the upper surface of housing 10. In other words, handle 41 pivots freely around handle shaft 42 over the range of motion of operation member 41a in handle insertion hole 13. An arcuate cover piece 41b is formed at the base of operation member 41a of handle 41 with handle shaft 42 as its center, and housing 10 is bulged outward in the area around handle insertion hole 13 to conform to cover piece 41b. Cover piece 41b slidably contacts the inside surface of housing 10 and shuts out the inside of housing 10 to be invisible even when handle 41 is rotated. Lettering is provided on cover piece 14b to indicate the open/closed state of the breaker contacts with the operation of handle 41.

Link support member 41c is mounted on the lower surface of cover piece 41b, with shaft tabs 41d mounted on both sides of the bottom of link support 41c. Operation member 41a and link support member 41c protrude from cover piece 41b such that they bend on a line.

Additionally, handle 41 is energized to the left as viewed in FIG. 2, by a handle return spring 43 installed around the periphery of bearing 14.

One end of handle return spring 43 is secured at the right edge of cover piece 41b as seen in FIG. 1, and the other end at trip plate 44 of the switching device described below.

The switching device is made up of a trip plate 44, a generally Ushaped handle link 45, a latch plate 46, and a contact link 48. Shaft tabs 41d on handle 41 are inserted through the bearing holes 45a formed at the end of each leg of handle:link 45. Latch plate 46 is made up of flat plate-type stop plate 46a and a pair of guide members 46b that extend parallel to each other from the ends thereof. Handle shaft 42 is inserted through shaft openings 46c formed at the leading ends of guide members 46b. Trip plate 44 is pivotally supported in housing 10 by shaft pin 47, with both ends of shaft pin 47 being inserted in bearings 15 formed on the inner surfaces of body 10a and cover 10b. Contact link 48 is formed in a general U-shape, and has one leg member 48a inserted through link holes 45c, which are formed in the base portions of the two legs of handle link 45, and through guide holes 46d, which are formed in the two guide members 46b of latch plate 46. The other leg 48b of contact link 48 is inserted through shaft openings 33a provided in movable contact 33. A guide channel 16 curved to form a convex arc is formed below (as seen in FIG. 2), on the inside surface of body 10a.

Inserting the end of leg 48b of contact link 48 into this guide channel 16 results in the range of motion of contact link 48 being regulated by guide channel 16.

Movable contact 33 is furnished with movable contact point 32 on one end and spring receiver member 33b on the other end, and has shaft openings 33a, located between movable contact point 32 and spring receiver member 33b, into which shaft leg 48b of contact link 48 is inserted. Movable contact point 32 is formed at the angle created by bending one end of movable contact 33 into a general L-shape, with arc runner member 33d extending out past movable contact point 32 to the end. Mounted on spring receiver member 33b is a spring seat that is inserted into one end of contact pressure spring 34, a coil spring. The other end of contact pressure spring 34 is received in spring receiver recess 35, formed on the inner surface of body 10a. Stopper 36 is mounted on the inner surface of body 10a, facing the opening surface of spring receiver recess 35. Contact pressure spring 34 and spring receiver member 33b are inserted into the space between the inner surface of body 10a, in which spring receiver recess 35 is formed, and stopper 36. Spring receiver member 33b is energized toward stopper 36 by the spring force of contact pressure spring 34.

A trip plate 44 is formed into a shape wherein a first push pressure member 44b is mounted extending from the top end of base member 44a to one side, while a second push pressure member 44c extends downward from base member 44a, and in addition, arm 44d is provided extending from the edge on one side of base member 44a midway between the top and bottom in a direction generally perpendicular to base member 44a. Shaft pin 47 is inserted in the base portion of arm 44d such that trip plate 44 rotates freely around shaft pin 47. Moreover, hook notch 44e is formed in the upper edge of the leading end of arm 44d, while farther out toward the end of arm 44d than hook notch 44e, the top edge of arm 44d slopes so as to approach the bottom edge. Also, retainer notch 44f is formed on the side edge of base member 44a as an upward-cut, opening toward the side. Trip plate 44 is energized counter-clockwise (as seen in FIG. 2) by retaining one end of handle return spring 43 in this retainer notch 44f.

Latch plate 46 can be rotated freely with respect to housing 10 by handle shaft 42 and handle 41, but the range of movement of latch plate 46 with respect to handle 41 is regulated by the fact that leg 48a of contact link 48, which is inserted in handle link 45, is inserted in guide holes 46d of latch plate 46, and handle link 45 is pivotally supported on shaft tabs 41d of handle 41. Moreover, the lower edge of stop plate 46a of latch plate 46 can be engaged with hook notch 44e provided in trip plate 44. In the engaged state, latch plate 46 is prevented from being moved.

As described above, switching device 40, made up of handle 41, handle shaft 42, handle return spring 43, trip plate 44, handle link 45, latch link 46, shaft pin 47, and contact link 48, functions through the action of electromagnetic release device 50 or thermal release device 60 to cause the breaker contacts to open when excessive current passes through the main electrical path with the breaker terminals in the closed state.

Electromagnetic release device 50 is furnished with yoke 52 which is made of magnetic material formed in an upward-opening general U shape, with coil 51 disposed within the space inside yoke 52. Yoke 52 is furnished with a pair of side members 52a and 52b facing the two axial end surfaces of coil 51, and base member 52c, which passes below coil 51 and joins the interval between the two side members 52a and 52b. Retainer grooves 52d and 52e are formed in side members 52a and 52b, respectively. Coil 51 is disposed around cylinder-shaped coil tube 53, which is made of electrically insulating material. Flange 53a is formed in one piece at one axial end of coil tube 53, and a narrowed section 53b in which both the inside and outside diameters are smaller than those of an intermediate section in the axial direction is formed at the other axial end of coil tube 53.

Plunger 54, having a section where the diameter is larger than the inside diameter of narrowed section 53b, is disposed within the inside space of coil tube 53 such that it can move freely in the axial direction of coil tube 53. Fixed core 55 is mounted in coil tube 53 opposite plunger 54 at the flange 53a end of coil tube 53 such that a portion of it protrudes from coil tube 53. One-piece catch pin 54a is provided at one of the end surfaces in the direction of travel of plunger 54 such that it protrudes from the end surface of the narrowed section 53b of coil tube 53. Fastened at the other end is push pressure pin 57, which passes through fixed core 55 and protrudes from the end surface of coil tube 53 at its flange 53a end. Formed at the leading end of catch pin 54a is catch pin head 54b, the diameter of which is larger than at other locations on the pin. Return spring 56, made from a coil spring, is installed between plunger 54 and fixed core 55, plunger 54 being energized toward the narrowed section 53b end of coil tube 53 by the spring force of return spring 54.

The ends in the direction of travel of plunger 54 are formed with a smaller diameter than the intermediate section, one end being spring receiver 54c which is inserted into return spring 56, and the other end formed to be inserted into the narrowed section 53b of coil tube 53, the intermediate section being formed with a diameter that is larger than that of the narrowed section. In other words, pull-out stopper step 54d is formed on plunger 54, between the large diameter section and the small diameter section with catch pin 54a on it, and plunger 54 is prevented from falling out by the fact that pull-out stopper 54d is retained by a step formed on the inner circumference of coil tube 53 between the intermediate section and narrowed section 53b.

Fixed core 55 is formed such that its end near the axial end of coil tube 53 near plunger 53, which has a smaller diameter than other locations, becomes spring receiver 55a, which is inserted into return spring 56, and outer collar member 55b, which has a larger diameter than other locations, is formed on the other end. Coupler 55c is mounted at the center of the other end. When fixed core 55 is inserted into the flange 53a end of coil tube 53, outer collar member 55b contacts the end surface of coil tube 53, and coupler 55c protrudes from the end of coil tube 53. Also, push pressure pin 57, attached to plunger 54, protrudes from coil tube 53 due to its being inserted through insert opening 55d, which passes through fixed core 55 in the axial direction.

The core formed by installing plunger 54, fixed core 55, and return spring 56 in coil tube 53 as described above is installed in yoke 52 by inserting narrowed section 53b of coil tube 53 into retainer groove 52d provided in side member 52a of yoke 52, and by inserting coupler 55c of fixed core 55 into retainer groove 52e of side member 52b. Here, with the flange 53a of coil tube 53 being disposed between coil 51 and side member 52b of yoke 52, insulation between coil 51 and side member 52b of yoke 52 is assured. Moreover, because coupler 55c is inserted in retainer groove 52e provided in side member 52b of yoke 52, and outer collar 55b is sandwiched between flange 53a of coil tube 53 and side member 52b, fixed core 55 is magnetically coupled to yoke 52.

Electromagnetic release device 50, constituted as described above, is secured in position on body 10 by inserting retainer tabs 17a and 17b mounted on the inner surface of body 10a into retainer grooves 52d and 52e provided in yoke 52, as illustrated in FIG. 4 and FIG. 5. In addition, yoke 52 is secured to body 10a by fitting side members 52a and 52b of yoke 52 into yoke 52 installation grooves 18a and 18b formed on the inner surface of body 10a near retainer tabs 17a and 17b. With yoke 52 secured to body 10a, narrowed section 53b of coil tube 53 and coupler 55c of fixed core 55 are supported between the inner peripheries of retainer grooves 52d and 52e, and the outer edges of retainer tabs 17a and 17b, and coil tube 53 is fixed in position with respect to yoke 52.

In an electromagnetic release device 50 constituted as described above, if current flows through coil 51, a pulling force will be created between fixed core 55 and plunger 54 so as to reduce the reluctance of the magnetic path through fixed core 55, yoke 52, and plunger 54, and if the current flowing in coil 51 is excessive in the event of a shorted load and the like plunger 54 will move toward fixed core 55 against the spring force of return spring 56. Accordingly, during such operation, the closed breaker contacts can be forcibly opened by operating switching device 40, switching device 40 being connected as described below.

The leading end of catch pin 54a provided on plunger 54 is inserted through catch opening 33e formed at a location between shaft openings 33a of movable contact 33 and movable contact point 32.

When plunger 54 is drawn toward fixed core 55 as a result of magnetic excitation of coil 51, catch pin head 54b on the leading end of catch pin 54a catches on the rim of catch opening 33e, pulling movable contact 33 away from fixed contact 31. Catch opening 33e is formed as an oblong hole connecting a stop hole having a diameter smaller than that of catch pin head 54b, and a guide hole having a diameter larger than that of catch pin head 54b. This configuration allows electromagnetic release device 50 to easily be linked to movable contact 33 during assembly by guiding catch pin 54a into the stop hole after catch pin head 54b has been passed through the guide hole. Moreover, the tip of push pressure pin 57, which is attached to plunger 54, is positioned facing second push pressure member 44c of trip plate 44 such that trip plate 44 will be rotated around shaft pin 47 in the clockwise direction (as viewed in FIG.

2) when plunger 54 is drawn into motion by fixed core 55.

On the other hand, thermal release device 60 is furnished with bimetal 61. One end of bimetal 61 is attached to terminal bar 21b, and the other end has adjustment screw 62. Adjustment screw 62 faces first push pressure member 44b of trip plate 44, positioned such that when bimetal 61 bends due to excessive current flowing in the main electrical path, the tip of adjustment screw 62 pressing against trip plate 44 causes trip plate 44 to rotate around shaft pin 47 in the clockwise direction (as seen in FIG. 2).

Adjustment window 63 is provided in an outer periphery wall of housing 10 near adjustment screw 62 at the upper end of bimetal 61.

Adjustment window 63 is furnished at the upper end with insertion section 63a formed with a width greater than that of the other parts.

The upper edge of adjustment window 63 forms guide surface 63b, which slants downward toward the inside of housing 10. As shown in FIG. 6, installation channels 63c are formed on both side surfaces of adjustment window 63, connected to insertion section 63a at their top ends, and extending to the bottom of adjustment window 63 at their lower ends. In other words, guide ribs 63d extending to the lower end of adjustment window 63, except for insertion section 63a, are formed on both sides of adjustment window 63 at the outside surface of housing 10, and guide ribs 63e extending the full length of adjustment window 63 from top to bottom are formed on the inside surface of housing 10, thus forming installation channels 63c between guide ribs 63d and 63e.

The degree to which bimetal strip 61 bends from the electrical current passing through it (its operating sensitivity) depends on variations in the composition of the material used and the location at which connecting wire 38 is connected. Therefore, in order to eliminate variations in the operating sensitivity of switching device 40 (i.e., the current flowing in the main electrical path when switching device 40 operates), it is necessary to adjust the amount adjustment screw 62, which is threaded into bimetal strip 61, protrudes from bimetal strip 61 on the trip plate 44 side. Accordingly, after assembly, adjustment screw 62 is operated with adjustment window 63 open. On the other hand, since once adjustment screw 62 has been adjusted, there is no need to make any further adjustments to adjustment screw 62, closure plate 64, which is flexible, is dropped into installation channel 63c through insertion section 63a, so that adjustment window 63 will be closed by closure plate 64 to prevent adjustment screw 62 from being inadvertently operated, and to prevent foreign matter from entering housing 10.

Closure plate 64 is set to be generally equal to the width of adjustment window 63 (the distance between the bottoms of installation channels 63c), and generally equal to the height dimension from top to bottom of adjustment window 63. When such a closure plate 64 is inserted into adjustment window 63, the upper edge of closure plate 64 hits the upper edge of adjustment window 63, and closure plate 64 cannot be removed.

As shown in FIG. 2, line terminal 20a and load terminal 20b are made up of terminal clamps 22a and 22b, which are formed by bending electrically conductive sheet metal, clamp screws 23a and 23b provided on the terminal clamps, and terminal plates 21a and 22b provided which butt against the lower ends of the clamp screws. The terminal clamps are received in square horizontal cross-section terminal chambers 24a and 24b formed in housing 10, such that the terminal clamps can be moved up and down. In other words, the height dimension of terminal chambers 24a and 24b is greater than that of terminal clamps 22, and terminal chambers 24a and 24b fit tightly around terminal clamps 22a and 22b, thus allowing the clamps to be move only up and down. The heads of clamp screws 23a and 23b are formed in a truncated cone shape, with the diameter at the top smaller than that at the bottom, and screw access holes 25a and 25b, having a diameter that will allow a portion of the heads of the clamp screws to be inserted therein, but will prevent the heads of clamp screws 23 from passing through, are formed in the upper walls of terminal chambers 24a and 24b. The di up and down, terminal plates 21a and 21b will remain in place even if acted on by external force from clamp screws 23. Here, the distance from terminal plates 21a and 21b to the upper walls of terminal chambers 24a and 24b is set to be generally equal to the length dimension of clamp screws 23.

When the tip of a common screwdriver, etc., is inserted in screw access holes 25a and 25b and clamp screws 23a and 23b are turned, terminal clamps 22a and 22b move up or down, depending on the direction in which the clamp screw is rotated, and the distance between the terminal clamp lower member and terminal plates 21a and 21b can be changed.

In other words, electrical connections to wiring material such as wire, bus bars, etc. can be made by inserting the wiring material through the connection holes 28 provided in the peripheral wall of housing 10 at locations corresponding to the spaces between the terminal plates 21a and 21b and the lower walls of the terminal chambers 24a and 24b, and turning the clamp screw to bring the lower members of the terminal clamps closer to terminal plates 21a and 21b, thus clamping the wiring material between the terminal clamps and terminal plates 21a and 21b.

/p.13/Terminal plate 21a, which is part of line terminal 20a, has a fixed contact plate 39 which is bent downward at a point inside of housing 10 from terminal plate retainer groove 27. Fixed contact 31 is attached at the lower end of fixed contact plate 39. Facing fixed contact point 31 is movable contact point 32, which is on movable contact 33. A portion of arc runner 71, which is made of conductive sheet material, is lapped on the surface to which fixed contact point 31 is mounted, below fixed contact point 31 on fixed terminal plate 39. Arc runner 71 is furnished with vertically oriented guide member 71a which overlaps a portion of fixed contact plate 39. The lower end of guide member 71a continues through inclined member 71b, which slants downward at an angle, to arc suppresser member 71c, which extends along the bottom wall of housing 10 to a point below base member 52c of yoke 52. Here, arc suppresser grid 72 is disposed between locations on base member 52c of yoke 52 and arc suppresser member 71c that face each other. Arc suppresser grid 72 has a configuration wherein a plurality of arc suppresser plates 74, made of electrically conductive sheets, are supported generally parallel to each other on the inside of support bracket 73, which is made of an insulating material, generally U-shaped.

Formed in each arc suppresser plate 74 is a cutout 74a into which the lower end of movable contact 33 is received. This arc suppresser grid 72 is disposed such than arc suppresser plates 74 are generally parallel to base member 52c of yoke 52 and arc suppresser member 71c of arc runner 71. The shape of arc suppresser member 71c of arc runner 71 is formed such that its width increases in steps as the distance away from inclined member 71b increases.

When movable contact 32 separates from fixed contact 31 as shown in A of FIG. 8 and an arc is created, then due to the surrounding magnetic field created as a result of the current flowing through terminal plate 21a and movable contact 33, and due to the magnetic force generated by the arc current, the arc will travel downward in the drawing, one end of the arc running along arc runner 71 toward arc suppresser grid 72. In other words, since fixed contact plate 39 on terminal plate 21a faces movable contact 33, and since the currents flowing in fixed contact plate 39 and movable contact 33 are flowing in opposite directions, an electromagnetic force will act upon the arc in a direction so as to pull it away from fixed contact plate 39 and movable contact 33. As a result, the fixed contact plate 39 end of the arc will run along arc runner 71 and be guided to arc suppresser grid 72. Since arc runner 33d is formed on movable contact 33, the other end of the arc will run toward the tip of arc runner 33d. In this manner, the arc is gradually guided to arc suppresser grid 72 while being stretched out in the process.

However, a portion of connecting wire 37, which connects movable contact 33 to one end of coil 51, is welded to side member 52a of yoke 52 closer to the breaker contacts. Therefore, when one end of the arc runs along arc runner 71, being guided to arc suppresser grid 72, the other end of the arc moves from arc runner member 33d of movable contact 33 to base member 52c of yoke 52, as shown in B in FIG. 8, causing a current to flow in a path going through base member 52c of yoke 52, side member 52a of yoke 52, connecting wire 37, and coil 51.

Because the direction of the current flowing in this path is opposite to that in arc runner 71, the magnetic field generated by the currents flowing in base member 52c of yoke 52 and in arc runner 71 is such that the arc receives an electromagnetic force guiding it into arc suppresser grid 72. In other words, intermediate member 52b of yoke 52 is capable of dual functions: it forms a magnetic path in electromagnetic release device 50, and it also functions with arc runner 71 to suppress arcs.

Thus the parts count is reduced in comparison to configurations where a pair of arc runners is provided, thereby simplifying structure and reducing cost.

As shown in FIG. 9, inclined arc travel promotion surfaces 19 are formed on both side walls of'housing 1, at the location in which arc runner 71 is disposed, such that the intervening distance between the walls spreads out in the direction away from the breaker contacts.

Moreover, the walls that sandwich the breaker contacts between themselves are closed off at the end opposite arc suppresser grid 72.

Accordingly, when the breaker contacts open, creating an arc, the arc gas pressure distribution is as indicated by the broken lines in FIG. 9, the highest pressure being near the breaker contacts and lowest being near arc suppresser grid 72. As a result, the arc gas is caused to flow toward arc suppresser grid 72. This flow of arc gas in the advancing direction of the arc serves to guide the arc quickly into arc suppresser grid 72.

As can be seen in FIG. 3, an installation mechanism is provided on the lower surface of housing 10 to allow the circuit breaker to be fastened to an installation rail 80 (called a DIN rail), within a power distribution panel, etc., such that it can be freely attached to and removed from the rail. Installation rail 80 is formed to have a U-shaped cross section, with outward-facing flanges 80a that extend the full length of the rails formed at the outer edges of both foot members. An installation notch 81 is formed on the lower surface of housing 10, with retainer lip 82 provided on one side wall of installation notch 81. One of the flanges 80a on installation rail 80 is inserted between retainer lip 82 and the floor of installation notch 81. Moreover, through-hole 83, which passes through to the outside surface of housing 10, is formed in the side wall at the other end of installation notch 81. Slider 84 is inserted into this through-hole 83. One end of slider 84 is furnished with rectangular frame 84a, which protrudes from the outside surface of housing 10, and the other end is furnished with finger 84b, which extends into the inside of installation notch 81. Provided on frame 84a are spring members 84c, which have free ends on one end of their finger 84b ends. Formed at the leading ends of spring members 84c are latches 84d, which have V grooves. The latches are stopped by steps formed on the inside surface of through-hole 83 (not illustrated), which enables slider 84 to be selectively held in a locked position, in which finger 84b extends to the inside of installation notch 81, or a released position, in which it is retracted. In the locked position, the other flange 80a of installation rail 80 is held sandwiched between finger 84b and the inner bottom surface of installation notch 81, thus securing the circuit breaker to installation rail 80. To remove housing 10 from installation rail 80, the tip of a common screwdriver, etc., if inserted into frame 84a, which is protruding at the side of housing 10, so as to pull slider 84 out of housing 10, finger 84b will be disengaged from flange 80a of installation rail 80, making it possible to remove housing 10 from installation rail 80.

Operation of circuit breaker will be described. FIG. 6 shows the circuit breaker in the "on" state (contacts closed), operation member 41a of handle 41 thrown around handle shaft 42 to the right. At this time, trip plate 44 is energized counterclockwise (as viewed in FIG. 6) around shaft pin 47 by the spring force of handle return spring 43, thus holding first push pressure member 44b in contact with adjustment screw 62 in bimetal strip 61. Moreover, the spring force of contact spring 34 is being applied via movable contact 33 and contact link 48 to latch plate 46, and, because the distance between leg 48a of contact link 48 and shaft tabs 41d on handle 41 is regulated by handle link 45, latch plate 46 receives the spring force of contact pressure spring 34 such as to energize it in the counterclockwise direction with handle shaft 42 as the center of rotation. Accordingly, stop plate 46a of latch plate 46 is engaged in hook notch 44e in arm 44d of trip plate 44. In other words, the state shown in FIG. 6 is maintained because although latch plate 46 is trying to rotate to the right, it is being prevented from doing so by latch plate 46. In this state, latch plate 46 is held in position by shaft handle 42 and trip plate 44, and handle link 45 and contact link 48 are also fixed in their proper positions. As a result, movable contact 33 is energized in the counterclockwise direction, centered around leg member 48b of contact link 48, by the spring force of contact pressure spring 34, and movable contact 32 is contacting fixed contact 31 with a pressure corresponding to the spring force of contact pressure spring 34.

In this state, the position relationship of stopper 36, provided on the inside surface of housing 10, is set so that it will not touch spring receiver member 33b of movable contact 33.

When, on the other hand, operation member 41a of handle 41 is thrown around handle shaft 42 to the left, as shown in FIG. 7, the circuit breaker will be in the "off" state (contacts open). In other words, rotating handle 41 around handle shaft 42 to the left moves the upper end of handle link 45 to the right, pulling leg member 48a of cont-act link 48 upward. When the location of shaft tabs 41d shifts to the right, relative to a line drawn between handle shaft 42 and leg member 48a, the spring force of contact pressure spring 34 being applied to handle link 45, through movable contact 33 and contact link 48, will act to move handle 41 further to the left, causing leg member 48b of contact link 48 to move to the left along guide channel 16. Moving leg member 48b of contact link 48 to the left in this manner results in spring receiver member 33b of movable contact 33 being pressed, by the spring force of contact pressure spring 34, against stopper 36, provided on the inside peripheral surface of housing 10. Here, since the spring force of contact pressure spring 34 is acting upon a point below the lower end of stopper 36, movable contact 33 is energized in the clockwise direction, and movable contact point 32 is separated from fixed contact 31. In the open state of the breaker contacts, latch plate 46, regulated by handle link 45 and leg member 48a of contact link 48, turns counter-clockwise with handle shaft 42 as its center of rotation, and is disengaged from trip plate 44.

When, however, in the closed contact state shown in FIG. 6, an overload causes excessive current to flow in bimetal strip 61, causing bimetal strip 61 to bend, adjustment screw 62, which is threaded into bimetal strip 61, will be pressed against first push pressure member 44b of trip plate 44, or if excessive current flows in coil 51 due to a short, etc., on the load side, plunger 54 will be drawn into fixed core 55, pushing push pressure pin 57, which is attached to the plunger, against second push pressure member 44c of trip plate 44. In either case, trip plate 44 will rotate clockwise, as shown in FIG. 8, with shaft pin 47 as its center of rotation. Rotation of trip plate 44 clockwise disengages it from latch plate 46, and since in the closed contact state, latch plate 46 receives the spring force of contact pressure spring 34, which energizes it in the clockwise direction around handle shaft 42, the lower end of latch plate 46 moves to the left. In other words, leg 48b of contact link 48, which, in the closed contact state, was the center of rotation of movable contact 33, moves to the left along guide channel 16.

Therefore, as in the open contact state shown in FIG. 7, movable contact 33 is pressed against stopper 36 by the spring force of contact spring 34, movable contact 32 is separated from fixed contact 31, and the circuit breaker assumes the open contact state. Hence, if excessive current flows in the main electrical path, trip plate 44 rotates, disengaging it from latch plate 46. This releases the energy being stored by latch plate 46, thereby performing the so-called tripping operation, to open the breaker contacts.

Embodiment 2 As shown in FIG. 10, this embodiment discloses step-shaped depressions 19a formed in the travel promotion surfaces 19, rather than the flat travel promotion surfaces formed on the side walls of the space within which arc runner 71 was disposed, as in the first embodiment.

When steps such as these are formed in travel promotion surfaces 19, the portion of the travel promotion surfaces 19 that is exposed to arcs is reduced. Thus, even where travel promotion surfaces 19 are deteriorated as a result of the heat of arcing, in locations where the degree of exposure to arcs is small, the degree of deterioration will also be small. This means that the degree of deterioration of travel surfaces 19 as a whole can be reduced, enabling the function of travel surfaces 19 to be extend over a longer service life than with the configuration of the first embodiment. Other constitution and operation information is the same in the first embodiment, and its explanation is therefore omitted.

LIST OF REFERENCE NUMERALS 10 housing 10a base 10b cover 17a retainer prong 1 7b retainer prong l9a stepped depression 20a line terminal 20b load terminal 31 fixed contact (breaker contact) 32 movable contact (breaker contact) 50 electromagnetic release mechanism (means) 51 coil 52 yoke 52a side member 52b side member 52c base member (second arc runner) 52d retainer groove 52e retainer groove 53 coil tube 53a flange 54 plunger 54 plunger 71 (first) arc runner 71 c extension

Claims (9)

1. CLAIMS: 1. A circuit breaker comprising: a pair of breaker contacts (31,32) disposed in a main current path extending between a line terminal (20a) and a load terminal (20b), said breaker contacts composed of a first contact (31) and a second contact (32); electromagnetic release means which detects an excess current flowing through said main current path and disengages said second contact (32) forcibly from said first contact (31), said release means comprising a coil (51) inserted in said main current path and a plunger (54) surrounded by said coil, said plunger being magnetically connected to said coil through a yoke (52), said yoke (52) being of a generally Ushaped configuration having a base member (52c) and a pair of side members (52a,52b) at opposite ends of said base member; a pair of opposed first and second arc runners (71,52c) disposed to guide an arc, which develops between said breaker contacts (31,32) upon separation thereof, in a direction away from said breaker contacts (31,32) by an electromagnetic force acting on said are in a magnetic field produced by a resulting arc current, said first arc runner (72) electrically connected to said first contact (31) and extending away therefrom to give an extension (71c), said second are runner (52c) electrically connected to said second contact (32) and extending away therefrom; said circuit breaker characterized in that: said yoke (52) is disposed to be electrically connected to said second contact (32) at the side member (52a) adjacent to said second contact (32) and to have said base member (52c) extending in opposed relation to said extension (71c) such that said base member (52c) itself defines said second arc runner.
2. 2. A circuit breaker as set forth in claim 1, wherein said coil (51) surrounds a coil tube (53) of electrically insulative material, said coil tube (53) having an electrically insulative flange (53a) at its one axial end thereof, said flange (53a) interposed between said coil (51) and the one side member (52b) of the yoke (52) located away from said breaker contacts.
3. 3. A circuit breaker as set forth in claim 1 or 2, wherein said coil (51) surrounds a core member including said plunger (54), and wherein said yoke (52) is formed in said side members (52a,52b) respectively with retainer grooves (52d,52e), said retainer grooves opening to the circumferences of said side members for receiving the opposite ends of said core member, said retainer grooves (52d,52e) also receiving retainer prongs (17a,17b) projecting on an interior surface of a breaker housing (10) in such a manner as to grip each one of the opposite ends of said core member between the periphery of each said retainer groove (52d,52e) and each said retainer prong (17a,17b).
4. 4. A circuit breaker as set forth in claim 1, 2, or 3, wherein said coil (51) surrounds the coil tube (53) formed at one axial end thereof with a narrowed section (53b) of which inside diameter is smaller than that of an intermediate section of said coil tube (53), and wherein said plunger (54) having a portion of which outside diameter is greater than the diameter of said narrowed section (53b) and less than that of said intermediate section so that said plunger (54) is axially movable within said coil tube (53), said coil tube (53) provided at the other axial end thereof with a fixed core (55), a return spring (56) being disposed between said fixed core (55) and said plunger (54), said fixed core (55) having a portion projecting outwardly of said coil tube (53), said coil tube (53) secured at its one axial end to said one side member (52a) of said yoke (52) , and said fixed core (55) magnetically coupled to the other side member (52b) of said yoke (52) at said projecting portion.
5. 5. A circuit breaker as set forth in any of claims 1 to 4, wherein said arc runners being confined within a space between opposed side walls of a breaker housing, a width of said space between said opposed side walls becoming greater towards the advancing direction of said arc.
6. 6. A circuit breaker comprising: a pair of breaker contacts (31,32) disposed in a main current path extending between a line terminal (20a) and a load terminal (20b), said breaker contacts composed of a first contact (31) and a second contact (32); electromagnetic release means which detects an excess current flowing through said main current path and disengages said second contact (32) forcibly from said first contact (31); and a pair of opposed first and second arc runners (71,52c) disposed to guide an arc, which develops between said breaker contacts (31,32) upon separation thereof, in a direction away from said breaker contacts (31,32) by an electromagnetic force acting on said arc in a magnetic field produced by a resulting arc current, said arc runners being confined within a space between opposed side walls of a breaker housing, said circuit breaker characterized in that: a width of said space between said opposed side walls becomes greater towards the advancing direction of said arc.
7. 7. A circuit breaker as set forth in claim 6, wherein the side walls of said breaker housing are formed with stepped depressions (19).
8. 8. A circuit breaker as set forth in claim 6 or 7, wherein at least one of said first and second arc runners (71,52c) is formed with an incline (71b) along which a distance to the opposed arc runner (52c) becomes greater in a direction away from said breaker contacts (31,32).
9. 9. A circuit breaker substantially as hereinbefore described with reference to the accompanying drawings.