CIRCUIT BREAKER

Abstract: Disclosed is a mechanism for automatically performing the resetting of a magnetic tripping device (9) in a circuit breaker in the following manner. The movement of a hook (3) linked with a handle (2) in the tripping operation is detected by a linkage member (11) and transmitted to a reset lever (13). Thus, a plunger (10) of the magnetic tripping device is returned into its reset position by the reset lever immediately upon the completion of the tripping operation. In the resetting operation of the handle, the linkage member detects the recovery of the hook into its initial position and returns the reset lever into initial position.

Description: CIRCUIT BREAKER The present invention relates to a circuit breaker, and more particularly to an automatic reset mechanism for a magnetic tripping device in a circuit breaker. In order to achieve a tripping operation by using a weak signal from an overcurrent detector circuit, generally, an electronic circuit breaker is provided with a magnetic tripping device constituted by a permanent magnet, a plunger arranged to be attracted to the permanent magnet, a tripping coil adapted to be excited in the direction to cancel the magnetic flux of the permanent magnet when the coil is energized, and a release spring for urging the plunger in the tripping operation. The magnetic tripping device is arranged such that the plunger is normally held in its reset position by the force due to the magnetic flux of the permanent magnet against the force of the releasing spring, while in the tripping operation, the magnetic flux of the permanent magnet is cancelled by the magnetic flux induced by a signal current flowing in tripping coil so that the plunger is moved to its tripping position by the force of the releasing spring. The movement of the plunger is transmitted to a tripping memeber in the circuit breaker to thereby achieve the tripping operation. After the magnetic tripping device has been once actuated, therefore, it is necessary to cause the plunger to come back to its reset position from its tripping position by an ex eternal force in order to recover the state in which the magnetic tripping device can perform the tripping operation. As a mechanism for resetting such a magnetic tripping device, there have been proposed a technique employing the movement of a handle of the circuit breaker and another technique employing the movement of a contact arm which carries a movable contact of the circuit breaker. According to the first-mentioned technique, a plunger of the magnetic tripping device is moved to its reset position through a resetting arm which is in contact with an end of the handle of the circuit breaker, when the handle is caused to come back to its reset position upon the completion of tripping operation of the tripping device. This technique is disclosed in U.S. Patent 3,826,951 issued to Alfred E. Mater et al. In the magnetic tripping device according to this technique, however, the resetting is performed by converting a slight displacement of the handle of the magnetic tripping device from its off-position to its reset position, and, therefore, the escape of a resetting member can not be obtained from the stroke of the plunger upon completion of resetting, so that the resetting member may interfere with the plunger in the tripping operation. It is necessary, therefore, to drive not only a latch member for tripping but the resetting member in the tripping operation, resetting in a problem that the tripping operation is made to be heavy so as to cause maloperations. In the latter technique, the movement of the contact arm is transmitted to the plunger of the magnetic tripping device through a lever rotatably supported at its center portion onto a bracket fixed to the magnetic tripping device, so as to cause the plunger to come back its reset position. This technique is disclosed in U.S. Patent 3,530,414 issued to Howard A. Wagner. According to this technique, a member of the contact arm for supporting a contact on/off mechanism, the magnetic tripping device, and a resetting mechanism are attached separately from each other, so that accuracy and strictness are required in constituent parts and in adjusting work respectively. There is a further problem that deformation may be caused in the constituent parts due to shocks by the high-speed operation of the mechanism and by an excessive force due to overstroke, resulting in maloperations. Thus, in the conventional resetting mechanism, a slight displacement is detected to drive the resetting mechanism or the movement of a part energized by an excessive force is transmitted to drive the resetting mechanism, and therefore there has been a serious problem in reliability in each case. An object of the present invention is to provide a circuit breaker provided with a circuit breaker tripping mechanism having a long life and high reliability with less maloperation and an automatic resetting mechanism adapted to surely perform the resetting of the magnetic tripping mechanism immediately upon the comple- tion of tripping operation thereof. According to the present invention, the circuit breaker comprises an actuator capable of assuming selected one of a first-and a second states and capable of being actuated by a magnetic force to change its state from the first one to the second one, a hook restrictionfrelease mechanism capable -of being actuated in response to the actuation of the actuator to release a hook from a hook restriction state in which the hook is restricted by the mechanism, a first spring member, a second spring member arranged such that the acting force thereof is changed in response to the actuation of the hook restriction/release mechanism, and an operating means for moving the actuator to the first state from the second state in response to the breakdown of a balanced state of force between the first and second spring members. The present invention will be apparent from the following detailed description taken in conduction with the accompanying drawings, in which: Fig. 1 is a longitudinal cross-section showing the arrangement of a circuit breaker according to a first embodiment of the present invention; Figs. 2, 3 and 4 are longitudinal crosssections showing a main part of the arrangement of the circuit breaker according to the first embodiment of the present invention when the breaker is in its normal current conduction state, in its tripping state, and in its reset state, respectively; Figs. SA to 5D are front views showing the various states of engagement between a hook and a trip fittings in the first embodiment of the present invention; Figs. 6A to 6E are front views showing the operation steps of a resetting mechanism in the first embodiment of the present invention; ; Figs. 7A and 73 are longitudinal cross-sections of a magnetic tripping device in the first embodiment of the present invention; Fig. -8 is a front view showing a second embodiment of the present invention; Fig. 9 is a front view showing a third embodiment of the present invention; Figs. 10 and 11 are front views showing a fourth embodiment of the present invention; Figs. 12A and 12B are front views showing a fifth embodiment of the present invention; Figs. 13A and 133 are front views showing a sixth embodiment of the present invention; Fig. 14A is a perspective view showing the shape of a reset lever, a guide and a pin in the first embodiment of the present invention; and Figs. 14B to 14F are side views showing various modifications of the shape of the reset lever, the guide and the pin. Referring to the drawings, the embodiments of the present invention will be described hereunder. Fig. 1 is a longitudinal cross-section showing the entire arrangement of a circuit breaker according to a first embodiment of the present invention. In a insulator casing 1, a primary and a secondary conductor 12a and 12b are provided in the proximity of the bottom of the casing. The primary conductor 12a is provided with fixed contacts 22 and the secondary conductor 12b is passed through a current transformer 7 provided as a current detector means for each phase and fixedly attached to the casing 1 by screws 64. A contact on/off mechanism 24 provided with a movable contact 21 is provided between the primar and secondary conductors 12a and 12b and the movable contact 21 is electrically connected to the secondary conductor 12b through a flexible conductor 67. Terminals 12c and 12d are attached to the primary and secondary conductors 12a and 12b respectively by screws 64. The contact on/off mechanism 24 is provided with a movable frame 70 rotatably supported by an axle 65 and urged clockwise in the drawing by a not-shown torsion spring and an insulator shaft 66 which connects the movable frames of the respective phases to inter link them to one another. A lower member of 83 of a toggle link is rotatably supported at its one end by an axle 68 on the movable frame 70 substantially at the center portion thereof and rotatably supported at its other end by axle 84 on an upper member 75 of the toggle link. The upper member 75 of the toggle link is supported at its one end by an axle 72 on a hook 3 substantially at the center portion thereof. A handle lever 81 is rotatably supported by an axle 71 fixedly attached to a fixed frame 76. The handle lever 81 is provided at its upper portion with an engage portion 81a which engages with a handle 2. The engagemant portion Bla is provided with a pin 81b. A spring 82 is provided between the pin 81b and the axle 84 so as to perform the snap action of the toggle link in the on/of f operation. The hook 3 for performing the tripping operation is formed into an inverted L-shape. The hook 3 is rotatably supported at its one end by an axle 73 on the movable frame 70 at an upper portion thereof and urged counterclockwise in the drawing by a not-shown spring. The hook 3 is formed at its other end with a tip end 3a which engages with a trip fitting 4. The externally operated handle 2 is mounted on the engagement portion 81a of the handle lever 81 and arranged to slidably engage with the actuator opening portion of the casing 1 from the inside thereof. In this embodiment, the movable contact 21 is divided into a main movable contact portion 78a for current conduction and an auxiliary movable contact portion 21a for current- cut-off which are fixedly attached to a main movable contact base 78 and an auxiliary movable contact base 21 respectively on the respective surfaces thereof opposed to the fixed contacts 22. The main movable contact base 78 and the auxiliary movable contact base 21 are rotatably supported by an axle 69 on the movable frame 70 and urged by springs 80 and 79 respectively to obtain contact pressures between the movable and fixed contacts. Although the movable contact is divided into the main and auxiliary movable contact portions because the embodiment relates to a circuit breaker of the type for cutting off a large current, it is not necessary to divide the movable contact in the case of a circuit breaker of the type for cutting off a small current. The fixed frame 76 is fixedly attached to the bottom of the casing, and the axle 71 of the handle lever and a movable frame stopper 74 are fixedly attached to the fixed frame 76. A reinforcing plate 70a is fixedly attached to the movable frame 70 at a portion thereof which is in contact with the stopper 74. Arc chutes 23 are provided about the contact portion. An insulator plate 77 is provided between the arc chutes 23 and the primary terminal 12c to prevent an arc from flying to the primary terminal 12c. A current signal detected by the current transformer 7 is applied to a tripping circuit 8 constituted by an electronic circuit, converted into a tripping signal, and then applied to an actuator or magnetic tripping device 9. The tripping circuit 8 may be that disclosed in Japanese Patent publication No. 25696/ShoSS (1980) or may be a tripping circuit of any other known electronic circuit breaker. A tripping mechanism 25 is constituted by the magnetic tripping device 9, the fitting 4 which serves as a tripping member, a pawl receiver 5 which serves as a transmission member, a lever 11 which serves as a linkage member, a reset lever 13, a tension spring 14 which verves as a reset lever holding member, and a compression spring 15 which serves as a reset lever urging member. Further, a tripping button 20 is provided for checking tripping or manually performing the tripping operation. Figs. 2, 3 and 4 show the positional relations among the respective constituent components of the tripping device in its normal current conduction state, in its tripping state, and in its reset state, respectively. Figs. SA to SD show the arrangement and operation of the pawl 6, the pawl receiver 5 and the tripping fitting 4. In the normal current conduction state, as shown in Fig. SA, a transmission portion 6b of the pawl 8 is at a standstill at the position as shown in the drawing due to the balanced state of force between the compression spring 85 and the tension spring 86. The tripping fitting 4 and the pawl receiver 5 are urged counterclockwise in the drawing by a torsion spring 84 wound around an axle 32. The pawl receiver 5 is prevented from rotating beyond the position as shown in the drawing by a stopper 88. The tripping fitting 4 is prevented from rotating beyond the position as shown in the drawing by a stopper 89 provided on the pawl receiver 5. For the sake of simplicity of figure, the compression spring 85, the tension spring 86, the torsion spring 87, and the stoppers 88 and 89 are omitted in Figs. SB to SD. Figs. SB to SD show the positional relation and operation of the pawl 6, the pawl receiver S and the tripping fitting 4, in the normal current conduction state, at the initiation of tripping operation, and at the initiation of resetting operation, respectively. The pawl receiver S is provided with a stopper 34 for stopping a lower end portion 4d of the tripping fitting 4 and rotatably supported by an axle 31 such that it is engaged by a stopper 6a provided at the pawl 6 in the normal current conduction state and in the reset state. The tripping fitting 4 is formed with an engagement portion 4a which engages with the tip end portion 3a of the hook 3, slot portions 4b and 4c, and the lower end portion 4d. The slot portion 4b serves to prevent interference when the tip end portion 3a of the hook 3 is engaged with the engagement portion 4a in the normally current conduction state and in the resetting operation. The slot portion 4c is formed substantial into a U-shape and the axle 32 is loosely passed through the slot portion 4c. The lower end portion 4d is slidably in contact with the stopper 34 so as to facilitate the disengagement of the hook 3 in the tripping operation and the reengagement of the hook 3 in the resetting operation. The pawl 6 is rotatably supported by an axle 30 and provided with the abovementioned stopper portion 6a and the transmission portion 6b provided perpendicularly to the stopper portion 6a for transmitting the movement of a pin 10a of the magnetic tripping device 9. Further, the pawl 6 is provided with another transmission portion 6c extending in the direction substantially perpendicular to the firstmentioned transmission portion 6b and in the direction in opposite to or different substantially by 1800 from the stopper portion 6a, for transmitting the movement of the tripping button 20 (Fig. 2). As shown in the best way in Fig. 2, the lever 11 is formed substantially into an L-shape and rotatably supported substantially at its center portion by an axle 32. The lever 11 is provided at its upper end portion with an abutment portion lla which engages with the hook 3 and provided at its lower end portion with a hole lIb to which a tension spring 14 is attached. The reset lever 13 is rotatably supported by an axle 33 in this embodiment as shown in the best way in Fig. 2, and provided with a hole 13a to which a tension spring 14 is attached, an opening or loose-fit portion 13b through which the pin lOa is loosely passed and another opening of loose-fit portion 13c through which a guide 63 is loosely passed as shown in the best way in Fig. l4A. The guide 63 is disposed in parallel with the pin lOa of the magnetic tripping device 9 and has one end provided with a stopper 61 and the other end attached to a plate 62. The guide 63 is provided with a compression spring 15 which serves as a reset lever urging means for urging the reset lever 13 toward the magnetic tripping device 9. The lever ll and the reset lever 13 are coupled with each other by the tension spring 14 so that the movement of the lever 11 is transmitted to the reset lever 13 through the tension spring 14. A plunger 10 of the magnetic tripping device 9 is provided with the pin 10a at its tip end. An abutment plate 40 provided on the pin 10a as an engagement portion engages with the loose-fit portion 13b of the reset lever 13 to thereby drive the pin lOa in the resetting direction. Figs. 7A and 7B show the internal arrangement of the magnetic tripping device 9, the former showing the reset state and the latter showing the state in tripping operation. In the magnetic tripping device 9, a casing is constituted by a frame 41 of a magnetic material and a yoke 42. A coil 45 and a permanent magnet 43 are provided in the casing and the plunger 10 of a magnetic material is inserted into the central portion of a bobbin 46 of the coil 45. The movement of the plunger 10 is transmitted outside through a guide 44. A compression spring 47 is provided between a flange portion 49 of the plunger 10 and the bobbin 46 so as to urge the plunger 10 outerward or left in the drawing. The operation of the magnetic tripping device 9 is as follows: Normally, that is when the coil 45 is not energized, the bottom of the plunger 10 is attracted to the frame 9, as seen in Fig. 7A, by the force due to the magnetic flux passing through the frame 41, against the force of the compression spring 47. If a tripping current is supplied to the coil 45 from the tripping circuit 8, the coil 45 produces magnetic flux in the direction in opposite to that of the permanent magnet 43 so as to cancel the attraction force between the plunger 10 and the frame 41. For this, the plunger 10 is urged by the compression spring to move left in the drawing until it reaches th position at which it is in contact with the guide 44, as seen in rig. 7B Referring to Figs. SB to SD, Fig. 6A to EE, and Figs. 7A and 7B, the steps of tripping operation according to this embodiment will be now described. For the sake of simplicity, the manual tripping button 20 and the transmission portion 6c are omitted in Figs. SB to SD and Figs. 6A to 6E. In the normal current conduction state, as shown in Figs. 53 and 6A, the tip end portion 3a of the hook 3 is engaged with the engagement portion 4a of the tripping fitting 4 and pushes the abutment portion lla of the lever 11. In this state, the lever 11 pulls the reset lever 13 through the tension spring 14 to thereby compress the compression spring 15 through the reset lever 13. The reset lever 13 stays at a position beyond the stroke of the abutment plate 40 due to the balance of force between the tension spring 14 and the compression spring 15. The lower end portion 4d of the tripping fitting 4 is supported by the stopper 34 provided on the pawl receiver S and the upper portion of the pawl receiver S is engaged with the stopper 6a, so that the tripping fitting 4 maintains the engagement with the hook 3. In tripping, a tripping current is supplied to the magnetic tripping device 9 from the tripping circuit 8t so that the plunger 10 is urged by the spring 47 to move toward the yoke 42, as shown in Fig. 7B. Thus, the pin 10a provided at the tip end of the plunger 10 is urged in the direction of arrow A as shown in Fig. 6 to be in contact with the transmission portion 6c. Further, as shown in Fig. 6C, the pawl 6 is rotated in the direction of arrow B to thereby release the engagement between the stopper 6a and the pawl receiver 5. The hook 3 is urged in the direction of arrow D by a spring (not shown) for urging the tripping mechanism 24 so that the hook 3 pushes up the tripping fitting 4, as shown in Fig. SC, against the urging force of the spring 87 to cause the tripping fitting 4 to rotate in the direction of arrow C, whereby the hook 3 releases the engagement with the tripping fitting 4 to trip the tripping mechanism 24. Upon the completion of tripping, the tripping fitting 4 and the pawl receiver S are caused to come back to their initial positions by being urged by the spring 87. At this time, the pushing force by the hook 3 is not acted on the abutment portion lla of the lever 11 so that the lever 11 is enabled to rotate in the direction of F as shown in Fig. 6D and the reset lever 13 is urged in the direction E by the recovery force of the compression spring 15 to move, while pushing the abutment plate 40 by its loose-fit portion 13b, until the reset lever 13 reaches the position at which it is in contact with the stopper 61. Thus, the plunger 10 is pushed back to its initial position in which it is attracted onto the frame 41 again by the force due to the magnetic flux of the permanent magnet 43, so that the magnetic tripping device 9 is made to reset. At this time, the pawl 6 is returned to its initial position by the springs 85 and 86. Under the condition, the breaker is in its tripped state and the handle 2 stays in its trip position as shown in Fig. 3. The breaker may be reset from this state by moving the handle 2 to its reset position as shown in Fig. 4. By this handle actuation, the hook 3 is urged in the direction of arrow H as shown in Fig. 5D and the tip end 3a of the hook 3 obliquely hits and pushes the engagement portion 4a of the tripping fitting 4. The tripping fitting 4 slides in the direction of arrow G by the pushing force of the tip end 3a of the hook 3 because the axle 32 is loosely inserted through the U-shaped slot portion 4c of the tripping-fitting 4. Further, the hook 3 moves in the direction of arrow H so as to be engaged again with the engagement portion 4a, so that the reset mechanism comes back into the state of Fig. 6A through the state of Fig. 6E. At this time, the hook 3 pushes the abutment portion lla of the lever 11 and the movement of the lever 11 is transmitted to the reset lever 13 through the tension spring 14 to cause the reset lever 13 to move to the position beyond the stroke of the abutment plate 40 to return into its initial state. According to this embodiment, the reset lever 13 is standing-by at the position beyond the stroke of the pin lOa without preventing the movement of the pin lOa during the tripping operation of the magnetic tripping device, so that a small driving force is sufficient to drive the pin lOa and the apparatus can be reduced in size as well as in weight. Further, although the lever 11 is pushed by the hook 3 in the normal state and in the reset state, the pushing is released in tripping and the rotation of the lever at this time is used to obtain a predetermined reset force to drive the reset mechanism. Further, there is an effect that the parts are hardly deformed and have long lifetime. Fig. 8 shows a second embodiment of the present invention. In this embodiment, a return spring 15 is provided on the pin IOa to thereby eliminate the guide 63 of the first embodiment. In this embodiment, the stroke of the return spring 15' may be reduced to small value so that a margin is provided in the stress of the return spring 15'. Fig. 9 shows a third embodiment of the present invention. In this embodiment, a tension spring 15U is provided as the reset lever urging member. Fig. 10 shows a fourth embodiment of the present invention. In this embodiment, a torsion spring 50 is provided as the reset lever urging member. Further, as shown in Fig. 11, a torsion spring 51 may be used with a reset plate 52 provided on the guide plate 62 as the reset lever, so that the position adjusting work can be simplified in assembling. Fig. 12A shows a fifth embodiment of the present invention. In this embodiment, a reset lever 53 is arranged to move horizontally, so that the movement of the reset lever 53 can be minimized and the apparatus is reduced in size to be accommodated within a narrow space. Further, one of the guides 63 can be eliminated as shown in Fig. 12B. In the latter case, although the tension spring 14 is exerted with a bending force when it is passed through the guide plate 62, the spring 14 is not deformed because it has elasticity; Fig. 13A shows a sixth embodiment of the present invention. In this embodiment, a reset plate 54 made of an elastic material is provided as the reset lever. The arrangement of the reset plate is not limited to that shown in Fig. 13A but it may be arranged as a reset plate 54' as shown in Fig. 13R. According to the sixth embodiment, the arrangement is simplified so that steps of assembling are reduced to thereby reduce the apparatus in size as well as in weight. The elastic material may be a spring plate or a soft synthetic resin plate. In this case, a reinforcement (not shown) may be provided at the attaching portion of the tension spring 14 when the situation requries. Figs. 14B to 14F show various modifications of the loose-fit portion between the reset lever and the guide and the loose-fit portion between the reset lever and the pin. The shape of the loose-fit portion between the reset lever and the guide is not limited to that shown in Fig. 14A but, as shown in Figs. 14B to 14D, the guide is formed into a channel-like guide 63 so that the upper end of the reset lever 13 may be used as it is as the loose-fit portion 13c' with the guide 63W or the upper end portion of the reset lever 13 formed with notches may be used as the loose-fit portion 13c" with the guide 63'. Further, as shown in Figs. 14E and 14F, the guide may be formed into a strip-like guide 63" with the upper end portion provided with a groove as the loosefit portion 13Cm . Further, as shown in Figs. 14D and 14F, the loose-fit portion between the reset lever and the pin 10a may be in the form of a slot 13b', so that the workability can be improved in assembling. The lever 11 may be used also as an actuator lever for an alarm switch (not shown) provided in the apparatus. The present invention is not restricted to the embodiments disclosed in this specification but all the modifications included in the scope of invention indicated in the appended claims are included in the present invention.

Claims: CLAIMS: 1. A circuit breaker comprising: an actuator (9) capable of assuming selected one of a first and a second state and capable of being actuated by a magnetic force to change its state from said first one to said second one; a hook restriction/release mechanism (4) capable of being actuated in response to the actuation of said actuator to release a hook (3) from a hook restriction state in which said hook is restricted by said mechanism; a first spring member (15); a second spring member (14) arranged such that the acting force thereof is changed in response to the actuation of said hook restriction/release mechanism; and an operating means for moving said actuator to said first state from said second state in response to the breakdown of a balanced state of force between said first and second spring members. 2. A circuit breaker having a tripping mechanism, said mechanism comprising: a magnetic tripping device (9); a tripping force transmitting means (lOa) connected to said magnetic tripping device and slidably provided; a transmission member (6) driven by said tripping force transmitting means; a tripping means (4) driven by said transmission member; a linkage means (11) rotatably provided on said tripping means and arranged such that said linkage means is pushed by a hook (3) linked with an actuator handle (2) when said hook is engaged with said tripping means; a reset lever (13) loose-fittingly provided on said tripping force transmitting means; reset lever holding means (14) provided between said reset lever and said linkage means for holding said reset lever with resiliency; ; reset lever urging means (15, 15', 15", 50, 51) for urging said reset lever in the direction to reset said magnetic tripping device; an engage portion (40) provided on said tripping force transmitting means for making engagement with said reset lever; and said reset lever being arranged such that said reset lever is disposed in a position beyond a stroke of said engage portion in a stand-by state of said tripping mechanism, while, in tripping operation, said reset lever is urged in said reset direction by said reset lever holding means and said reset lever urging means in response to the actuation of said linkage means. 3. A circuit breaker according to claim 2, in which said reset lever urging means (15') is loose-fittingly provided on said tripping force transmitting means (lOa). 4. A circuit breaker according to claim 2, in which said reset lever urging means includes a tension spring (15"). 5. A circuit breaker according to claim 2, in which said reset lever urging means includes a torsion spring (50, 51). 6. A circuit breaker according to claim 2, in which said reset lever is slidably loose-fittingly provided on a guide means (63) mounted in parallel with said tripping force transmitting means as well as said tripping force transmitting means. 7. A circuit breaker according to claim 2, in which said reset lever is made of an elastic material.

Inventors: MORIYA, SHIGEO
Applicants: HITACHI, LTD.
Application year: 1984
Main classification: H01H71
IPC codes: H01H73, H01H71