FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
& THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
CIRCUIT BREAKER;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. 1

Technical Field
[0001]
The invention relates to a circuit breaker equipped with an electromagnetic tripping device using an oil dash pot, in particular the electromagnetic tripping device improve the driving force for the switching mechanism unit trip.
Background Art
[0002]
In a conventional circuit breaker electromagnetic device composed of an electromagnetic tripping device of a circuit breaker, along with oil dash pot type of the iron core fixed on one of the legs of the L~shaped yoke made of a magnetic plate, the movable iron piece is rotatably supported to face the contacting surface on the fixed core to the other leg, the movable iron piece is maintained to fit the window hole or the notch of the movable iron piece in the pole part of the yoke.
The spring is provided for biasing the movable iron piece to enlarge the gap between the respective contacting pole surfaces of the movable iron piece and the fixed iron core.
Further, one end of the iron core provided in the oil dash pot of the fixed iron core is coupled to one leg of the L~shaped yoke to form the magnetic circuit, the attracting force closing the magnetic circuit rotates the movable iron piece and then cause to operate the switching mechanism unit.
[0003]
In such a device, while maintaining the load tripping device of the mechanism unit, when the size of the electromagnetic tripping device is minimized, it is possible that the attraction force for tripping the electromagnetic tripping device becomes not sufficient.
Therefore, instead of changing the number of turns of the coil that make up the electromagnetic device that affect the anti-time limit characteristic of the circuit breaker, for the purpose of increasing the attraction force, the bent part of the yoke being formed by means that the tip of the other leg of the yoke is bent to the fixed iron core side, thereby due to the expansion of the contracting surface based on the bent part, the electromagnetic tripping device with improved attraction force is known (for example, see Parent Literature 1).
Patent Literature [0004] [Patent Literature] JP2001-307614 A (cf. Fig. 5) Disclosure of Invention
Technical Problem
[0005]
In a conventional electromagnetic tripping device regarding to the circuit breaker as described above, while maintaining the trip load of the switching

mechanism unit, when the electromagnetic tripping device is organized in a downsized configuration, it is possible that the driving force for tripping the electromagnetic tripping device becomes not sufficient.
[0006]
The present invention made to solve the problems as described above, is a circuit breaker which can increase the driving force regarding to an electromagnetic tripping device for the tripping of the switching mechanism unit without upsizing of the electromagnetic tripping device.
Solution to Problem
[0007]
According to the present invention, in a circuit breaker which is provided by a movable contact arm, a stationary contact arm fixed in contact to the movable contact arm, a switching mechanism unit for opening and closing the movable contact arm, an electromagnetic tripping device tripped to the switching mechanism unit connected to the movable contact arm, the electromagnetic tripping device is composed of a magnetic plate and a yoke, a fixed iron core fixed to one of the leg of the yoke, the iron core is wounded around, a coil connected in series with both contacts, and rotates freely held by the holding part of the other leg of the yoke, a movable iron piece having a pole contact area on the electrode surface of the fixed iron core, the fixed end part is fixed in the fixed end holding part of the yoke that is separated from its position, the movable iron piece spring maintained in the movable iron piece on the free end part, when the movable iron piece is not attracted to the fixed iron core, the free end part of the movable iron piece spring, relating to the connection between the fixed end part of the movable iron piece spring and the movable iron piece, when the movable iron piece located in the first position of the yoke is not attracted by the fixed iron core, the fixed end part of the movable iron piece spring of the movable iron piece is connected to the free end part of the movable iron piece spring from the position 1 to the position 2.
Advantageous Effects of Invention
[0008]
According to the present invention, when the fixed iron core attracts the movable iron piece, since the biasing force of the movable iron piece spring is added to the attraction force by magnetic force, it is possible to maintain the driving force for the trip of the switching mechanism unit, thereby it is possible to plot the miniaturization of the circuit breaker according by the miniaturization of the electromagnetic tripping device.
Brief Description of Drawings [0009]
[Fig. 1] According to the first embodiment of the present invention, Fig 1 is a longitudinal sectional view showing the overall configuration of the circuit breaker.
[Fig. 2] According to the first embodiment of the present invention, Fig 2 is an enlarged side view of an electromagnetic tripping device.

[Fig. 3] In the enlarged view of the yoke of the electromagnetic tripping device shown in Fig. 2, (a) is a side enlarged view, (b) is a front enlarged view. [Fig. 4] In the enlarged view of the movable iron piece of the electromagnetic tripping device shown in Fig. 2, (a) is a plan enlarged view, (b) is a side enlarged view.
[Fig. 5] Fig. 5 is an explanatory view of the operation of the movable iron piece spring when the movable iron piece is not attracted regarding to the electromagnetic tripping device shown in Fig. 2.
[Fig. 6] Fig. 6 is an explanatory view of the magnetic flux when the movable iron piece is not attracted regarding to the electromagnetic tripping device shown in Fig. 2.
[Fig. 7] Fig. 7 is an explanatory view of the magnetic flux when the movable iron piece is attracted regarding to the electromagnetic tripping device shown in Fig. 2.
[Fig. 8] Fig. 8 is an explanatory view of the operation of the movable iron piece spring when the movable iron piece is attracted regarding to the electromagnetic tripping device shown in Fig. 2.
[Fig. 9] According to the second embodiment of the present invention, Fig 9 is an explanatory view of the operation of the movable iron piece spring when the movable iron piece is not attracted regarding to the electromagnetic tripping device.
[Fig. 10] Fig. 10 is an explanatory view of the operation of the movable iron piece spring when the movable iron piece is attracted according to the electromagnetic tripping device shown in Fig. 9.
Description of Embodiments
[0010] Embodiment 1
According to the first embodiment of the present invention, Fig. 1 is a vertical sectional view showing the overall configuration of the circuit breaker, Fig. 2 is an enlarged side view of an electromagnetic tripping device, in Fig. 3 which is an enlarged view showing the yoke of the electromagnetic tripping device shown in Fig. 2, (a) is a side enlarged view, (b) is a front enlarged view, in Fig. 4 which is an enlarged view showing a movable iron piece of the electromagnetic tripping device shown in Fig. 2, (a) is a plan enlarged view, (b) is a side enlarged view, Fig. 5 is an explanatory diagram explaining the operation of the movable iron piece when the movable iron piece is not attracted by the electromagnetic tripping device shown in Fig. 2, Fig. 6 is an explanatory view of the magnetic flux when the movable iron piece is not attracted by the electromagnetic tripping device shown in Fig.2, Fig. 7 is an explanatory view of the magnetic flux when the movable iron piece is attracted by the electromagnetic tripping device shown in Fig. 2, Fig. 8 is an explanatory view of the operation of the movable iron piece spring when the movable iron piece is attracted by the electromagnetic tripping device shown in Fig. 2.
[0011]
According to Fig. 1, a case of the circuit breaker 101 is constructed by using a base 11 formed by insulating materials and a cover 12.

On the base 11, the circuit breaker units connected to the electric circuit (for example, 3 if it is a three-phases) are arranged in parallel with each other for each pole, the top part of the circuit breaker units of the center is arranged by the switching mechanism unit 30 using a delayed-action mechanism widely known.
[0012]
The cover 12 cover the switching mechanism unit 30 and all of the circuit breaker units on the base 11, the operation handle 31 of the switching mechanism unit 30 is protruding from the hole 12a of the cover 12.
Further, each phase of the circuit breaker unit is configured to be equal to each other, the cross bar 13 being common to each phase of the circuit breaker unit is mounted on the base 11 so as to be orthogonal to each phase of the circuit breaker unit.
[0013]
Each phase of each circuit breaker unit owns a power supply side terminal 20 which is the first external terminal provided by the base 11, a stationary contact arm 21 having a stationary contact 22 which is extendedly disposed and connected to the power supply side terminal 20, a movable contact 23 which contacts to and discontacts from the stationary contact 20, a movable contact arm 24 which has the movable contact 23 on one end part and is freely moved up and down held by the cross bar 13, an electromagnetic tripping device 40 which is connected through a flexible copped twisted wire 25 to the movable contact arm 14 and operates to trip the switching mechanism unit 30, and a load side terminal 26 being the second external terminal which is mounted on the base 11.
The movable contact 23 and the stationary contact 22 configures a switching contact for making and breaking an electric circuit.
Also, near the movable contact 23 and the stationary contact 22, an arc extinguishing unit 27 that owns an arc extinguishing plate 27a is provided.
If the movable contact 23 contacts with the stationary contact 22, the electrical circuit between the two terminals 20 and 26 is turned on, also, if the movable contact 23 is separated from the stationary contact 22, the electrical circuit between the terminals 20 and 26 is turned off.
[0014]
The crossbar 13 is moved up and down according by the switching mechanism unit 30, when the crossbar 13 is moved up and down, each of the movable contact arm 24 of the circuit breaker unit of each pole is moved up and down at the same time. According to the up and down moves of the movable contact arm 24, the movable contact 23 is in contact with the stationary contact 22 and is in discontact from stationary contact 22.
Also, a well-known drip bar 33 which is drove by the electromagnetic tripping device 40 of each pole is built in the switching mechanism unit 30.
[0015]
As shown in Fig. 2, the electromagnetic tripping device 40 is composed of a coil 41 which is connected to the load side terminal 26 and the movable contact arm 24 and wounded for the change of the magnetic flux by the passage of the electric current, the L~shaped yoke 42 being the electromagnetic plate which passes the magnetic flux of the coil 41, and an oil dash pot 43 which is fixed to one leg of the yoke 42 and determine the anti-time limit characteristic by

controlling the time during the ion core being attracted a pipe cover 45 because of the magnetic flux of the coil 41 according to the viscosity of the oil 46.
The oil dash pot 43 is provided with a pipe 44 around which the coil 41 is wounded, the pipe cover 45 that achieve the role of the cover of the pipe 44, the iron core 47 together with the oil 46 inside the pipe 44, and an iron core spring 48 which is provided between the iron core 47 and the pipe cover 45 and biases the iron core in a direction away from the pipe cover 45.
Further, the oil dash pot 43 above-mentioned is stated in the claims as "Fixed iron core,/.
[0016]
Further, the electromagnetic tripping device 40 owns the movable iron piece 49 held freely rotatably by the fixed end holding part 42a provided on the other leg of the yoke 42 and facing the pipe cover 45, and the movable iron piece spring 50 which is provided in the space between the end part 49e of the movable iron piece 79 and the bent part 42b of the yoke 42 and biases the movable iron piece 49. As shown in Fig. 3, the bent part 42b of the yoke 42 is provided by bending a part of the yoke from the vicinity of the fixed end holding part 42a.
[0017]
As shown in Fig. 4, the movable iron piece 49 owns an attraction surface 49a formed to the pipe cover 45, a fulcrum 49b which is a rotation axis of the movable iron piece 49, a pierce hole 49c for passing the extension part 42c of the yoke 42, a bent part 49d corresponding the pierce hole 49c for forming a magnetic circuit to the yoke 42, and a free end holding part 49el which is provided by the end part 49e of the movable iron piece 49 and holds the movable iron piece spring 50.
The movable iron piece spring 50 which is a compression spring is provided in the space of the free end holding part 49el and the fixed end holding part 42bl provided by the end part of the bent part 42b of the yoke 42. Here, the side of the fixed end holding part 42bl is a fixed end part 50a of the movable iron piece spring 50, the side of the free end holding part 49el is a free end part 50b of the movable iron piece spring 50.
[0018]
In a conventional electromagnetic tripping device, to maintain the anti-time limit characteristic of the circuit breaker, it is difficult to sufficiently increase the attraction force of the movable iron piece. Therefore, in the case of an AC current only, the switching mechanism unit used by the inertia of the movable iron piece which is caused by vibration based on the commercial frequency is tripped by the frequency of move of the movable iron piece.
On the other hand, if an electric circuit breaker having the conventional electromagnetic tripping device is applied to the DC circuit, as the movable iron piece doesn't oscillate, it is impossible to use the inertia of the movable iron piece as in AC circuit. Therefore, in the case that the electric circuit having the conventional electromagnetic tripping device is applied to DC circuit, it is necessary to change the number of turns of the coil, the viscosity of the oil, and/or the iron core spring.
[0019]

In order to solve this problem, in the present embodiment, the movable iron piece spring 50 has a compression spring, for the distance between the free end holding part 49el and the fixed end holding part 42bl become smaller than the distance between the fulcrum 49b and the free end holding part 49el, in other words, the fixed end holding part 42bl is created for the free end part 50b to be closer than the fulcrum 49b.
In a state where the following rating electric current is flowing in the electric circuit, as shown in Fig. 5, the free holding part 49el maintained by the free end part 50b of the movable iron piece spring 50 is on the side of the yoke 42 (right side of the Fig. 5) rather than the line A which connect the fulcrum 49b, that is the rotational axis of the movable iron piece 49, to the fixed end holding part 42c at which fixed end part 50a of the movable iron piece spring is maintained.
[0020]
From this state, if the free end part 50b and the free end holding part 49el rotates towards the line A, as the distance between the free end holding part 49el and the fulcrum 49b doesn' t change, the length LI of the movable iron piece spring 50 become smaller as the free end part 50b become closer to the line A, the movable iron piece spring 50 become more compressed. Therefore, in the free end part 50b, when the length LI of the movable iron piece spring 50 which is the compression spring become longer, the energization Fl works. In other words, the moment Ml in the counterclockwise direction of the force is generated around the fulcrum 49b. According by the moment Ml of this force, the energization of the attraction surface 49a of the movable iron piece 49, from the pole contact area of the pipe cover 45 become more distant, the end part 49e moves rotationally until it contacts the yoke 42.
Further, as described in the claims as the "first position,/ is the free end part 50b of the movable iron piece spring 50 that is placed on the side of the yoke 42 from the line A.
[0021]
The blocking operation of the circuit breaker 101 will be explained hereinafter.
If a current flows to the electric circuit, an exciting current flows to the coil 41, the magnetic flux generated by the exciting current is, as shown on Fig.6, passing through the magnetic circuit from the yoke 42-^iron core 47-^the magnetic gap Gl of the first space between the iron core 47 and the pipe cover 45—>the pipe cover 45, the magnetic gap G2 of the second space between the movable iron piece 49 and the pipe cover 45, the movable iron piece 49, the yoke 4. In this case, when the predetermined value of more of the excess current flows to the electric circuit, the magnetic flux produced by this excess current generates an absorption attracting the core 45 in the direction of the pipe cover 45, this attraction force exceed the urging force of the iron core spring 48. In this way, the iron core 47, as shown in Fig. 7, is attracted to the side of the pipe cover 45 through a predetermined time due to the viscosity resistance of the oil 46, the first magnetic gap Gl decreases as shown in Fig. 6 from the usual time L2 and the Fig. 7 from the usual time L3. By decreasing the first magnetic gap Gl where the iron core 47 is absorbed by the pipe cover 45,

the magnetic flux B of the second magnetic gap G2 of the space between the pipe cover 45 and the movable iron piece 49 gradually increases.
[0022]
When the energization of the movable iron piece 49 exceed the load by the movable iron piece spring 50, this increased absorption starts to rotate in a clockwise direction around the fulcrum 49b.
Then, the free end part 50b of the movable iron piece spring 50, when the fixed end holding part 42bl maintained by the fixed end part 50a of the movable iron piece spring and the fulcrum 49b which has the rotational axis of the movable iron piece 49 are connected on the line A, the movable iron piece spring 50 becomes on the most compressed state.
From this state, when the movable iron piece 49 rotate further in the clockwise direction to the line A and comes to the other side of the yoke 42 (left side of the Fig.8), as shown in Fig. 8, as the distance between the free holding part 49el and the fulcrum 49b doesn' t change, the movable iron piece spring 50 release a further compression state, it becomes possible to start an expansion, in the free end part 50b, the biasing force F2 of the length LI of the movable iron piece spring 50 that becomes longer works.
[0023]
In other words, the biasing force F2 generates a moment M2 in the clockwise direction of the force to the center of the fulcrum 49, the movable iron piece 49 is further rotated clockwise, according by the drip bar 33 pushed by the end part 49e, the cross bar 13 of the switching mechanism unit 30 is driven, the movable contact arm 24 is separated from the stationary contact arm 21.
According by the move of the movable contact arm 24, the stationary contact 22 is separated from the movable contact 23. When the movable contact 23 is separated, the arc generated by the flowing current is extinguished by the arc extinguishing part and the isolation is complete.
[0024]
In this case, the end part 49e of the movable iron piece 49 coming into contact with the trip bar 33 as soon as the free end part 50b rotates from the first position to the second position, crossing over the line A. In other words, the trip of the switching mechanic unit 30 according by the electromagnetic tripping device is done as soon as the free end part cross over the line A. Thus, by adding the absorption force by the moment M2 of the acting force to the movable iron piece 49, the driving force sufficiently exceeding the loading trip of the switching mechanic unit 30 is intended.
Regarding the On and Off action, since similar to the circuit breaker, the description thereof is omitted.
Therefore, the second position as stated in the claims is the inverse side of the yoke 42 where the free end part 50b of the movable iron piece spring 50 has moved from the position 1, crossing over the line A, in other words, it's the opposite side of the position of the first position relative to the line A.
[0025]
According to the present embodiment, the movable iron piece spring 50 has a compression spring, the fixed end holding part 42b is established close to the free end part 50b from the fulcrum 49b, moreover, when the movable iron piece 49

is not attracted by the oil dash pot 43, the free end part 50b of the movable iron piece spring 50 is on the side of the yoke 42 facing the line A, when the movable iron piece 49 is attracted by the oil dash pot 43, since the free end part 50b is on the opposite side of the yoke 42 by crossing over the line A from the yoke 42, if the oil dash pot 43 is tripped by the movable iron piece 49, the energization of the movable iron piece where the absorption force according by the magnetic flux is added, as the driving force where the movable iron piece 49 pushes the trip bar 33 increases, it becomes possible to miniaturizing the electromagnetic tripping device 40 by tripping the electric current and decreases the number of turns of the coil 41, it is possible to miniaturize the circuit breaker.
[0026]
Also, when the oil dash pot 43 attracts the movable iron piece 49, as the energization of the movable iron piece spring 50 is added by the absorption force according to the magnetic force, it is possible to achieve the common use of the electromagnetic tripping device 40 tripped by electric current of the AC or DC current.
[0027]
Therefore, in the present embodiment, although an example in which the stationary contact 22 is provided on the stationary arm contact 21 and the movable contact 23 is provided by the movable contact arm 24, but without providing the movable contact 23 or the stationary contact 22, the movable contact arm 24 and the stationary contact arm 21 are connected, so it is possible to have it in contact or separated.
[0028] Second Embodiment
Regarding an electromagnetic tripping device, Fig. 9 of the second embodiment of the present invention shows an explanatory view of the action of the movable iron piece spring when the movable iron piece is not attracted, regarding an electromagnetic tripping device as shown in Fig. 9, Fig. 10 is an explanatory view of the action of the movable iron piece spring when the movable iron piece is attracted.
In the first embodiment, the movable iron piece spring 50 of the electromagnetic tripping device 40 is organized by the compression spring, the electromagnetic tripping device is organized by a pulling spring of the movable iron piece spring.
[0029]
Regarding Fig. 9, an electromagnetic tripping device 60 is composed by a coil 61 wounded for the change to a magnetic flux of the passage electric current of the load side terminal 26 and the movable contact arm 24, a L shaped yoke 62 where passes the magnetic flux of the coil 61, the use of the magnetic flux of the coil 61 stuck to the other log of the yoke 62, an oil dash pot 63 is determined by the anti-time limit characteristic, by controlling the absorption time from the viscosity of the oil to the pipe cover. The oil dash pot 63 is composed by a pipe 64 wounded by the coil 61, a pipe cover 65 that takes the role of the cover of the pipe 64, a iron core 67 established to oil 66 and the pipe 64, is established in the space between the pipe cover 65 and the iron core

67, the iron core spring energized to keep away the iron core 67 to the pipe cover 65.
[0030]
Thus, the electromagnetic tripping device 60 is composed by the movable iron piece 69 maintained in a freely rotation according by the holding part 62a established to the other side of the yoke 62, in the opposite of the pipe cover 65, stretched in the space between the en part 69e of the movable iron piece 69 and the fixed end holding part 62b established by the yoke 62, the movable iron piece spring 51 energized by the movable iron piece 69.
[0031]
In addition, the yoke 62 is composed of the holding part 62a that maintain the movable iron piece 69, is established on the upper part of the holding part 62a, the fixed end holding part 62b maintained by the movable iron piece spring 51.
The movable iron piece 69 owns the absorption surface 69a attracted to the pipe cover 65, the fulcrum 69b that is the rotational axis of the movable iron piece 69, is established by the end part 69e of the movable iron piece 69, and the free end holding part 69el for maintaining the movable iron piece spring 51. [0032]
The movable iron piece spring 51 that is a pulling spring is stretched to the space between the free end holding part 69el and the fixed end holding part 62b of the yoke 62, the fixed end part 51a of the movable iron piece spring 51 is on the side of the fixed end holding part 62b of the fixed end part, the free end part 51b of the movable iron piece spring 51 is on the side of the free end holding part 69el of the free end part. Therefore, the distance between the free end holding part 69el and the fixed end holding part 62b is established as the distance of the fulcrum 69b and the free end holding part 69el is longer. The rest of the configuration is the same as in the first embodiment, so the description is omitted.
[0033]
Next, the operation is explained.
With the above configuration, in a state in which the following current rated value is flowing, as shown in Fig. 9, the fulcrum 69b that is a rotational axis of the movable iron piece 69 is connected to the fixed end holding part 62b maintained by the fixed end part 51a of the movable iron piece spring 51 to the line C, the free end holding part 69el and the free end part 51 of the movable iron piece spring 51 are on the side of the yoke 62 (right side of Fig. 9). [0034]
From this state, by moving rotatingly the free end part 51b and the free end holding part 69el to the line C, as the distance from the free end holding part 69el to the fulcrum 69b doesn' t change, the length of the movable iron piece spring 51 become longer as the free end part 51b become closer to the line C, the movable iron piece spring 51 is further extended.
Therefore, in the free end part 51b, when the length of the movable iron piece spring 51 that is a stretching spring becomes shorter, the biasing force F3 works.
[0035]

Therefore, the biasing force F3 of the movable iron piece spring generates the moment M3 of the counter clockwise force about the fulcrum 69b. According to the moment M3 of this force, the absorption surface 69a of the movable iron piece 69 is on the direction away from the pipe cover 65 that is the pole contact area, in other words, energized to the direction of the arrow D, the end part 69e rotates until touching the yoke 62.
Thus, the first position as stated in the claims is the position of the side of the yoke 62 where the free end part 51b of the movable iron piece spring 51 is, according to the line C.
[0036]
Next, the cutoff operation will be explained.
Like in the first embodiment, by flowing current, the excitation current flows to the coil 61, the magnetic flux according by this excitation current pass through the magnetic circuit composed of the yoke 62-^the iron core 67—» the first magnetic gap G3 in the space between the pipe cover 65 and the iron core 67—*the pipe cover 65—Hhe second magnetic gap G4 in the space between the pipe cover 65 and the movable iron piece 69-^the movable iron piece 69—Hhe yoke 62.
In this case, when the over current flows through a predetermined value or more to the electric circuit, the magnetic flux created by the overcurrent generates an absorption of the absorption force from the iron core 67 to the pipe cover 65, the absorption force cross over the biasing force of the iron core cover 68.
[0037]
Then, as shown in Fig. 10, the iron core 67 is attracted to the side of the pipe cover 65 through a predetermined time due to the viscosity resistance of the oil 66, the first magnetic gap G3 is reduced from L4 as shown in Fig. 9 to L5 as shown in Fig. 10.
[0038]
This increased absorption force, when the load of the energization of the movable iron piece 69 by the movable iron piece spring 51 is crossed, the clockwise rotation of the movable iron piece 69 to the fulcrum 69b starts. Then, the free end part 51b of the movable iron piece spring 51 comes to the top when the fulcrum 69b that is the axis of rotation of the movable iron piece 69 is connected to the line C with the fixed end holding part 62b, the movable iron piece spring 51 becomes in an extended state. From this state, the movable iron piece 69 exceeds the rotation to line C in the clockwise direction, when it comes to the opposite side of the yoke 62 facing the line C, as shown in Fig.10, as the distance from the fulcrum 69b to the free end holding part 69el doesn' t change, the movable iron piece spring 51 is released in a moreover extended state, the compression starts, in the free end part 51b, when the direction of the length of the movable iron piece spring 51 become shorter, the biasing force F4 works.
The second position as described in the claims, the free end part 51b of the movable iron piece spring 51 is in the opposite side of the yoke 62 moved from the first position to the line C, in other words, it is the position of the opposite side of the first position facing the line C
[0039]

Then, the biasing force F5 of the movable iron piece spring 51 generates a moment M4 in the clockwise direction of the force about the fulcrum 69b. According to the moment F4 of the force, the absorption surface 69a of the movable iron piece 69 become closer to the pipe cover 65 in the pole contact area, in other words, it is energized in the direction of the arrow E,' and its rotation is clockwise.
By this rotation, the end part 69e pushes the drip bar 33, the movable contact arm 24 which is driven by the cross bar 13 of the switching mechanism unit 30 is separated from the stationary contact arm 21.
When the movable contact 23 is separated, the arc generated by the flowing current is extinguished by the arc extinguishing unit 27, and the isolation is completed.
[0040]
In this case, the end part 69e of the movable iron piece 69 comes to contact with the drip bar 33, when the free end part 51b rotates from the first position to the second position crossing over the line C.
In other words, the tripping of the switching mechanism unit 30 according to the electromagnetic tripping device 60 is done when the free end part 51b crosses over the line C.
When the moment M4 of the working force gain an absorption force by the magnetic flux to the movable iron piece 69, when the charge of the tripped switching mechanism unit 30 is sufficiently up, the driving force is exerted.
[0041]
According to the present embodiment, a stretching spring is done by the movable iron piece spring 51, the fixed end holding part 62b is established near the free end part 51b, when the absorption of the movable iron piece 69 to the oil dash pot 63 is not done, the free end part 51b of the movable iron piece spring 51 is on the side of the yoke 62 facing the line C, when the absorption of the movable iron piece 69 to the oil dash pot 63 is done, the free end part 51b go from the side of the yoke 62 to the opposite site of the yoke 62 by crossing the line C, when the movable iron piece 69 is absorbed by the oil dash pot 63, the biasing force of the movable iron piece spring 51 is added to the absorption force according to the magnetic force, as the driving force increases when the movable iron piece 69 pushes the drip bar 33, it becomes possible to decreases the number of turns of the coil, to miniaturize the electromagnetic tripping device 60, consequently, the circuit breaker can also be miniaturized.
[0042]
In addition, when the movable iron piece 69 is absorbed by the oil dash pot 63, as the biasing force of the movable iron piece spring 51 is added to the absorption force according to the magnetic force, it is possible to share the electromagnetic tripping device 60 for DC and AC current.
Reference Signs List
[0043] 1 0 Case 1 1 Base
1 2 Cover
2 0 Power supply side terminal

2 1 Stationary contact arm 2 2 Stationary contact 2 3 Movable contact 2 4 Movable contact arm
2 6 Load side terminal
3 0 Switching mechanism unit
4 0 Electromagnetic tripping device 4 1 Coil
4 2 Yoke
4 2b Bent part
4 2 b 1 Fixed end part Fixed end holding part
4 3 Oil dash pot
4 9 Movable iron piece
4 9 e End part
4 9 e 1 Free end part Free end holding part
5 0 Movable iron piece spring) 5 0 a Fixed end part
5 0 b Free end part 1 0 1 Circuit breaker

We Claim :
[Claim 1] A circuit breaker comprisinga movable contact arm, a stationary-contact arm connected or separated from the movable contact arm, a switching mechanism unit which is connected to the movable contact arm and open and close the movable contact arm, an electromagnetic tripping device tripped by the switching mechanism unit, wherein
the electromagnetic tripping device hasa yoke composed of a magnetic plate, a fixed iron core fixed to one part of a leg of the yoke, a coil wounded to the fixed iron core and connected in series with both the contact arms, a movable iron piece whichis held rotatablyby holding part of another part of the leg of the yoke and owns anattraction surface facing an attraction area of the fixed iron core, and a movable iron piece spring of which fixed end part is hold by a fixed end holding part of the yokein the position separated from the holding part and of which free end part is held by a free end holding part of the movable iron piece, and wherein
when the movable iron pieceis not attracted by the fixed iron core, the free end part of the movable iron piece spring is on the first position on the side of the yoke rather than a line connecting anaxis of rotationof the movable iron piece to the fixed end partof movable iron piece spring,
when the movable iron piece is attracted by the fixed iron core, the free end part of the movable iron piece spring comes from the first position to the second position crossing over the line.
[Claim 2] The circuit breaker according to the claim 1, wherein the movable iron piece is a compression spring, and the distance between fixed end holding part and the free end holding part is shorter than the distance between the free end holding part and the axis of rotation of the movable iron piece.
[Claim 3]The circuit breaker according to the claim 1, whereinthe movable iron piece is a stretching spring, the distance between the fixed end part and the free end holding part is longer than the distance betweenthe free end holding part and the axis of rotation of the movable iron piece.
[Claim 4]The circuit breaker according to any one of the claims 1 to 3, whereinthe trip of the switching mechanism unit by the electromagnetic tripping device is done when the free end part cross over the line.