Patent Publication Number: US-6903295-B2

Title: Fluid pressure operating apparatus for circuit breaker

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a circuit breaker, and it relates, in particular, to a fluid pressure operating apparatus for such the circuit breaker, being suitable as a circuit breaker for use of electric power. 
     An example of a conventional fluid pressure operating apparatus for use in a circuit breaker is shown, for example, in Japanese Patent Laying-open No. 2000-90784 (2000) &lt;JP-A 2000-90784&gt;. Such the operating apparatus as described in this publication has a piston for use of opening/closing of a contact, for the operating apparatus to bring the contact into open/close, and a control valve mechanism for actuating this, for preventing the contact from a pumping operation of repeating opening/closing operation thereof. The control valve mechanism has a switching valve and a switching control valve. The directional valve changes over the pressure onto a cylinder operation chamber of a piston for use of opening/closing of the contact. The switching control valve has a switching control valve for use of close (operation) and a switching control valve for use of open (operation). There is provided an anti-pumping piston for closing a check valve, and a conduit is connected to an anti-pumping piston operation chamber, which is branched from a portion between a secondary side of the switching controller valve for use of close (operation) and a primary side of the check valve. 
     In such the fluid operating apparatus as described in the Japanese Patent Laying-Open No. 2000-90784 (2000) mentioned above, a solenoid drives a pilot valve, and the pilot valve drives the directional control valve, respectively. And, the directional control valve operates a main valve for use of open (operation) and a main valve for use of close (operation). As a result of this, for actuating the piston for driving the contact, the valves are necessary in a large number thereof, thereby bringing about a large-size of the apparatus, as well as, a large number of parts thereof. Also, since the fluid flows directly into a return side of low pressure from a supply side during the operation of the directional control valve, this may be a factor of causing pressure fluctuation, and therefore it is strongly desired to reduce that. 
     BRIEF SUMMARY OF THE INVENTION 
     An object, according to the present invention made by taking the problems of the conventional arts mentioned above into the consideration thereof, is to provide the fluid pressure operating apparatus for a circuit breaker, being small in sizes thereof, and also simplified in the structure thereof. Other object, according to the present invention, is to improve reliability of the fluid pressure operating apparatus for a circuit breaker. 
     For accomplishing the object mentioned above, according to the present invention, first there is provided a fluid pressure operating apparatus, comprising: a fluid pressure cylinder for opening and/or closing a contact; control valves for use of open (operation) and/or close (operation), for bringing said fluid pressure cylinder into an opened-circuit operation and a closed-circuit operation; and driving portions, each being provided in each of those control valves, wherein said driving portions and said control valves are disposed in a same axis thereof. 
     And, according to the present invention, in the fluid pressure operating apparatus, as described in the above, preferably, said control valve is a poppet valve, and said driving portion is a solenoid of a type of direct movement. And, further preferably, a plunger owned by said solenoid and a valve body owned by said poppet valve have engagement portions, and each of those engagement portions has a length, so that it is longer at said valve body side than that at said plunger side. 
     Further, according to the present invention, for accomplishing the object mentioned above, there is also provided a fluid pressure operating apparatus, comprising: a fluid pressure cylinder for opening and/or closing a contact; control valves for use of open (operation) and/or close (operation), for bringing said fluid pressure cylinder into an opened-circuit operation and a closed-circuit operation; and solenoids, each being provided in each of those control valves, wherein each of said solenoid has a plunger therein, so that an operation initiating time of said control valves for use of open (operation) differs from that of said control valves for use of close (operation) when operating to open a circuit and when operating to close a circuit. 
     And, according to the present invention, in the fluid pressure operating apparatus, as described in the above, a penetrating hole may be formed in each of said control valves, within which said plunger is able to move, and a projection portion may be formed at a tip of said plunger, thereby to engage with said control valve at said projection portion, or both said plungers of said solenoid for driving the control valve for use of open (operation) and said solenoid for driving the control valve for use of close (operation) may be disposed on a same axis, and are neighboring with each other on a side opposing to said projection portions of said plungers. 
     Also, preferably, according to the present invention, in the fluid pressure operating apparatus, as described in the above, a penetrating hole may be formed in each of said control valves, within which said plunger is able to move, and a projection portion may be formed on each of said plungers, thereby engaging said projection portions with said control valves, and further two (2) pieces of said plungers are disposed on a same axis, and a connection rod is provide for connecting between the projection portions of said both plungers. Further, each of said control valves may be a poppet valve. Also, it is preferable that said control valve for use of open (operation) and said projection portion of the plunger engaging with said control valve for use of open (operation) are in contact with under a condition where said control valve for use of open (operation) is closed, while a gap is defined between said control valve for use of close (operation) and said projection portion of the plunger engaging with said control valve for use of close (operation) under condition where the plunger engaging with said control valve for use of open (operation) and said control valve for use of close (operation) are in contact with, on the other hand said control valve for use of close (operation) and said projection portion of the plunger engaging with said control valve for use of close (operation) are in contact with under a condition where said control valve for use of close (operation) is closed, while a gap is defined between said control valve for use of open (operation) and said projection portion of the plunger engaging with said control valve for use of open (operation) under condition where the plunger engaging with said control valve for use of close (operation) and said control valve for use of close (operation) are in contact with. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       Those and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a vertical cross-section view of an embodiment of the circuit breaker, according to the present invention; 
         FIGS. 2  to  4  are the vertical cross-section view for explaining the operation thereof; 
         FIG. 5  is a vertical cross-section view for showing a variation of the circuit breaker shown in  FIG. 1 ; 
         FIGS. 6 and 7  are the vertical cross-section views for explaining the operation of the circuit breaker shown in  FIG. 1 ; 
         FIG. 8  is a vertical cross-section view for showing other variation of the circuit breaker shown in  FIG. 1 ; and 
         FIG. 9  is a vertical cross-section view of other embodiment of the circuit breaker, according to the present invention, corresponding to FIG.  1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments according to the present invention will be fully explained by referring to the attached drawings, in particular the vertical cross-section views shown in  FIGS. 1  to  8 . Herein,  FIG. 1  is a view where the circuit breaker is in a condition of the closed-circuit thereof; i.e., during the conduction period thereof.  FIG. 2  shows an initial condition in an operation of open-circuit, and  FIG. 3  a condition in an internal period of the open-circuit, respectively.  FIG. 4  is a view for showing the closed-circuit condition thereof; i.e., the cut-off condition.  FIG. 5  shows the latter period of the open-circuit condition,  FIG. 6  an initial condition of the operation of closed-circuit thereof,  FIG. 7  a middle period of the operation of closed-circuit thereof, and  FIG. 8  a latter period of the operation of closed-circuit thereof, respectively. 
     The fluid pressure operating apparatus  3  for a circuit breaker comprises a fluid pressure cylinder portion  72  for opening and/or closing a contact portion  70 , a control valve  20  for use of open (operation) and a control valve  40  for use of close (operation), for changing over the pressurized fluid, which is supplied onto the fluid pressure cylinder portion  72 , and a driving portion  78 , having a pair of solenoids  60  and  80 , for driving those control valves  20  and  40 , respectively. The contact portion  70  has a movable contact  2  and a contact  1 , on which the movable contact  2  is on contact with. 
     The pressure cylinder portion  72  has a cylinder  4 , in which a cylinder space  7  is formed, for the movable contact  2  to move therein, and a piston  5 , which moves in an inside of this space  7 . The piston is attached onto a connecting rod  5   a . Neighboring to the pressure cylinder portion  72  is provided the control valve  20 . The control valve  20  and the driving portion  78  are disposed or aligned in a straight line-like manner. 
     On the driving portion  78  disposed at a center of the straight line, a solenoid  60  for use of open (operation) and a solenoid for use of close (operation) are disposed, fitting back to back thereof. At a central portion of each of those solenoid  60  and  80 , there is disposed a fixed core  63  or  83 , respectively, and through penetrating holes formed in the fixed core  63  and  83  can move a plunger  32  for use of open (operation) and a plunger  52  for use of close (operation), each of which has a disc portion  34  or  54 , respectively. On a side of an outer diameter of the fixed cores  63  and  83  are disposed coils  62  and  82  opposing to those fixed cores  63  and  83 , respectively. The plunger  32  for use of open (operation) and the plunger  52  for use of close (operation) fit to each other at a small diameter portion on a rear surface side thereof. 
     When current flows into the coil  62  of the solenoid  60  for use of close (operation), electromagnetic suction force is generated between the fixed core  63  and the plunger  32  for use of open (operation), and the plunger  32  for use of open (operation) narrows a gap  64 . On the contrary to this, when current of the solenoid  80  for use of close (operation) flows into the coil  82 , electro-magnetic suction force is generated between the fixed core  83  and the plunger  52  for use of close (operation), and then the plunger  52  for use of close (operation) narrows a gap  84 . 
     The control valve  20  for use of open (operation) and the control valve  40  for use of close (operation) are symmetric to each other. Thus, they have a container or vessel structure, each being opened to a side of the driving portion  78 , and they hold valve bodies  21  and  41  within housing  28  and  48 , each being formed with a penetrating hole at a center portion thereof. The valve bodies  21  and  41  have a stage-like structure, each having a cylindrical a portion  24  or  46 , having a small diameter at a side of the driving portion  78 , while at a neighboring side thereof have a cylindrical portion having a large diameter. End portions of those small diameter cylindrical portions  24  and  46  are attached to the housings  28  and  48 , hermetically. Corner portions of the large diameter cylindrical portions are formed to be taper-like, and are abutted onto valve seats, being corner portions of the stages of those housings. The penetrating holes formed in the valve bodies  21  and  41  are staged holes, on each of those staged portions abutting a projection portion  23  or  43 , which is formed at the tip of the plunger  32  or  52 . 
     On an end surface of the valve body  21  of the control valve  20  for use of open (operation) at the side of the driving portion  78 , the disc portion of the plunger  32  is in contact with at one end side thereof, on the other end side of which is disposed a second spring  31  in contact with the valve body  21 . On the other hand, so as to be in contact with the end surface of the control valve  40  at the side of the driving portion  78  and the housing  48  at both end portions thereof, a third spring is disposed. Further, on one side of an outer diameter of the second spring  31 , so as to be in contact with the housing  28  for use of open (operation) and the plunger  32  for use of open (operation) at both end portions thereof, a first spring  61  is disposed. 
     A space  7  within the cylinder  4  has a staged shape, and at the staged portion  7   b  can be fit a tip portion  5   b  of the piston  5 . Between a space  6  on a side of the moveable contact  2  within the space  7 , which is divided into two (2) by the piston  5 , and an inside of the housing  28  of the control valve  20  for use of open (operation), there is a conduit  102  communicating with each other. Also, a communication hole  103  is formed between the staged portion  7   b  of the space  7  and the staged portion  20   a  of the control valve  20  for use of open (operation), and a communication hole is between the staged portion  7   b  of the space  7  and the staged portion  40   b  of the control valve  40  for use of close (operation). Further, between the space  6  of the cylinder  4  and the staged portion  40   a  of the control valve for use of close (operation), there is a conduit  100  communicating with each other. 
     On way of the conduit  102  is provided an oil pressure pump  8 , which is driven by an electric motor, and an accumulator  9  is attached thereto, branching from this conduit. In the accumulator  9  is stored an operating oil of high pressure, which is pressurized by the oil pressure pump  8 . The conduit dividing in an upper stream of the oil pressure pump  8  is communicated to a reservoir  10  of low pressure. Into this reservoir  10  is collected a fluid discharged from the fluid pressure operating apparatus  3 , thereby to be stored therein. 
     Into the space  6  of the space  7  within the cylinder  4 , a supply pressure of high pressure of the operating fluid always acts, which is pressurized by the oil pressure pump  8  and accumulated in the accumulator  9 . On the other hand, into the other space  7   a  of the space  7  within the cylinder  4  is given a return pressure of low pressure from the supply pressure of high pressure or the reservoir  10 , selectively, by the valve function of the control valve  20  for use of open (operation) and the control valve  40  for use of close (operation). An area for receiving pressure of the space  6  is smaller than that of the space  7   a , by a cross-section area of the connecting rod  5   a , e.g., (πd 1   2 /4). 
     The control valve  20  for use of open (operation) is of a two-way valve. It communicates the space  7   a  of the cylinder  7   a  to the return side of low pressure, to push the piston downwards in  FIG. 1 , thereby opening the contact portion  70 . A diameter d 3  of the cylindrical portion  24  in the valve body  21  of the control valve  20  for use of open (operation) is smaller than the diameter d 4  of the valve seat  25 . A rear surface of the cylindrical portion  24  is opened to the atmospheric pressure. Under the condition of closed-circuit, the supply pressure for the difference of the area between the valve seat  25  and the cylindrical portion  24 ; e.g., {π(d 4   2 −d 3   2 /4), thereby holding the control valve  20  for use of open (operation) in the condition of being closed. 
     The control valve  40  for use of close (operation) is of a two-way valve of a poppet valve type. It communicates the space  7   a  of the cylinder to the supply side of high pressure, to push the piston upwards in  FIG. 1 , thereby closing the contact portion  70 . The diameter d 5  of the cylindrical portion  46  in the valve body  41  is smaller than the diameter d 6  of the valve seat  45 . 
     Operations in the embodiment being constructed in this manner will be explained, hereinafter. 
       FIG. 1  shows the condition of the closed-circuit. All of the space  6  of the cylinder, a secondary side space  40   b  of the control valve  40  for use of close (operation), communicating to the space  6  through the conduit  101 , a primary side space  40   a  communicating to the secondary side space  40   b , and a secondary side space  20   a  of the control valve  20  for use of open (operation) are high in the pressure. A primary side space  20   b  of the control valve  20  for use of open (operation) is low in the pressure. 
     Namely, the control valve  20  for use of the open (operation) is closed, and the secondary side space  20   b  is held at low pressure while at high pressure the staged portion  20   a , being the primary side space. In the control valve  40  for use of close (operation), the secondary side space  40   b  and the primary side space  40   a  are communicated with. The plunger  52  for use of close (operation) keeps moving into the left-hand side in  FIG. 1 , up to the position where the side surface of the disc portion  54  is in contact with the fixed core  83  of the solenoid  80 . Since the plunger  52  for use of close (operation) is moving into the left-hand side, the plunger  32  for use of open (operation) is also moving into the left-hand side. Also, through both of the spaces  6  and  7   a  within the cylinder  4  are kept at high pressure, since the pressure receiving area of the space  6  is smaller than that by the cross-section area of the connecting rod; e.g., (πd 1   2 /4), the piston  5  is pushed upwards. 
     The situation is shown in  FIG. 2  where an instruction of open-circuit is generated after the condition shown in this FIG.  1 . Upon the instruction of open-circuit, the coil  62  of the solenoid  60  for use of open (operation) is excited. Excitation of the coil  62  generates a force for suctioning the disc portion  34  of the plunger  32  for use of open (operation), and the gap  64  is shortened between the fixed core  63 . Accompanying with movement of this plunger  32  for use of open (operation), also the plunger  52  for use of close (operation) moves to the right-hand side. In this instance, since high voltage is applied to the plunger  52  for use of close (operation), it comes to be a resistance. Also, a friction force is generated, however the suction force of the plunger  32  is set to be a value overcoming those resistances thereof. 
     When the plunger  52  for use of close (operation) moves to the right-hand side, the valve body  41  of the control valve  40  for use of close (operation) moves to the right-hand side. As a result of this, the control valve  40  for use of close (operation) is closed. In this instance, between the side surface on the projection portion  23  of the plunger  32  for use of open (operation) and the staged portion on the valve body  21  of the control valve  20  for use of open (operation), a gap is defined. When the gap is defined in this manner, it is possible to prevent the plunger  32  from moving the valve body  21  for use of open (operation), even if the plunger  32  moves into the right-hand direction. Accordingly, it is possible to keep the control valve for use of open (operation) in the condition of being closed. Since both the control valve  20  for use of open (operation) and the control valve  40  for use of close (operation) are closed, it is possible to avoid blow-by from the side of the accumulator  9  of high pressure to the side of reservoir  10  of low pressure. 
     The situation is shown in  FIG. 3 , where the operation of open-circuit proceeds from the condition shown in FIG.  2 . The plunger  32  for use of open (operation) moves into the right-hand direction, and the projection portion  23  is in contact with the valve body  21  of the control valve  20  for use of open (operation). Under this condition, the plunger  32  moves the valve body  21 , further, into the right-hand direction, if the suction force of the solenoid  60  overcomes the sum of a force due to the pressure of operating fluid, which acts upon the difference of cross-section area; e.g., ΔS={π(d 4   2 −d 3   2 )/4}, between the valve seat  25  and the cylindrical portion  24  of the control valve  20  for use of open (operation). With this, the control valve  20  for use of open (operation) opens. 
     As is apparent from the equation of the difference of cross-section area ΔS, if the difference is small in the diameter between the valve set at  25  and the cylindrical portion  24 , the suction force comes to be small necessary for driving the plunger  32  for use of open (operation). The plunger  32  moves to the right-hand direction until when it abuts on the fixed core  63  of the solenoid  60  for use of open (operation) at the side surface thereof. Accompanying with this, the plunger  52  for use of close (operation) also moves to the right-hand direction, however the valve body  41  will not move since it comes out from the engagement with the plunger  52 , and then the control valve  40  for use of close (operation) keeps the condition of being closed. 
     When the control valve  20  for use of open (operation) is opened, the space  7   a  of the cylinder  4  is communicated to the reservoir  10  of low pressure through the staged portion  20   a  of the control valve  20  for use of open (operation). Since the space  7   a  goes down to low pressure, the force applying upon the piston from the side of the space  6 , upon which the high pressure is always applied, comes to be larger than the force, which is applied upon the piston from the side of the space  7   a , thereby pushing down the piston  5 . As a result of this, the connection between the movable contact  2  and the contact is broken down, thereby starting the operation of open-circuit. 
     The situation is shown in  FIG. 4 , where the piston  5  reaches to the bottom dead center thereof during the proceeding of the operation of open-circuit. The plunger  32  stays at the position where it moves due to the spring force of the first spring  61  even when a current instruction is cut off to the solenoid  60 . With this, the control valve  20  for use of open (operation) keeps the condition of opening, while the piston stays at the bottom dead center. 
     In the embodiment mentioned above, since the valve body  21  of the control valve  20  for use of open (operation) moves together with the plunger  32 , the valve body  21  can move only within a range of stroke of the plunger  32  by means of the solenoid  60 . However, as shown in  FIG. 5 , it is also possible to mover the valve body  21 , further, into the right-hand direction. 
     Upon the valve body  21  is applied the force of oil pressure directing from the right-hand side to the left-hand side, and this oil pressure force relates to the difference of cross-section area between the valve seat  25  and the cylindrical portion  24 . On the other hand, a fluid force acts upon from the left-hand side to the right-hand side due to the fact that fluid flowing passing through the communication hole  103  flows into the space  20   b  of the secondary side from the space  20   a  of the primary side. In the ordinary fluid pressure operating apparatus, the maximum moving position of the valve body  21  is determined, by bringing those forces into a balance thereof. If changing this balance by decreasing the force of oil pressure acting upon from the right-hand side to the left-hand side, then the valve body  21  moves to the right-hand direction, further. As is apparent from this, for letting the valve body  21  to move into the right-hand direction, further, it is sufficient to reduce the difference of cross-section area between the valve seat  25  and the cylindrical portion  24 . 
     In this manner, if making the moving stroke of the valve body  21  to be longer than that of the plunger  32 , the moving stroke of the plunger  32  may be short without matter. It is possible to actuate the piston  5  more speedy, or to actuate the piston  5  of a large diameter. 
     When the operation of open-circuit of the piston  5  is completed, flow of the operating fluid stops, and then no fluid force acts upon the valve body  21 . Since the fluid force comes to be zero, the valve body  21  moves into the left-hand direction due to a spring force of the second spring  31 . And, it stops the movement thereof when contacting with the projection portion of the plunger  32  for use of open (operation). This condition is the condition of close (operation) shown in FIG.  4 . 
     Further under the condition of open-circuit, the space  7   a  of the cylinder is communicated with the return side of low pressure. For this reason, the piston keeps the condition of open-circuit even if a very little leakage occurs in the control valve  40  for closed-circuit by any chance. The control valve  40  for closed-circuit is kept to be closed, due to force of the operating fluid upon the difference of cross-section area between the valve seat  45  and the cylindrical portion  46 . 
     The situation is shown in  FIG. 6 , where an instruction of closed-circuit is generated, under the condition of open-circuit shown in FIG.  4 . The coil  82  of the solenoid  80  for use of close (operation) is excited, and then a suction force generates between the disc portion  54  of the plunger  52  and the fixed core  83  of the solenoid  80  for use of close (operation). When this suction force overcomes the sum of a spring force of the third spring  51  and the friction force, a gap  84  between the disc portion  54  and the fixed core  83  is reduced. On the other hand, the plunger  32  for use of open (operation), being in contact with the plunger  52  for use of close (operation), spread out a gap  64  between the disc portion  34  of the plunger  32  for use of open (operation) and the fixed core  63  of the solenoid  60  for use of open (operation). 
     The valve body  21  of the control valve  20  for use of open (operation) and the plunger  32  for use of open (operation) are operated through a spring force of the second spring  31 . Therefore, when the plunger  32  for use of open (operation) moves towards the left-hand direction, the valve body  21  of the control valve  20  also moves towards the left-hand direction, thereby closing the control valve  20  for use of open (operation). It is preferable that a gap δ is formed between the projection portion  43  of the plunger  52  for use of close (operation) and the valve body  41  of the control valve  40  for use of close (operation) under this condition. When forming the gap δ in this manner, it is possible to bring both the control valve  20  for use of open (operation) and the control valve  40  for use of close (operation) into the closed condition. And, it is also possible to prevent the pressure from blowing by, from a side of the accumulator  9  of high pressure to a side of reservoir  8  of low pressure. When the plunger  32  for use of open (operation) and the plunger  52  for use of close (operation) move toward the left-hand direction further, the valve body  41  of the control valve  40  for use of close (operation) and the projection portion  43  of the plunger  52  for use of close (operation) are in contact with each other. 
       FIG. 7  shows the situation where the side surface of the disc portion  54  of the plunger  52  for use of close (operation) moves up to be in contact with the fixed core  83  of the solenoid  80  for use of close (operation). The suction force of the solenoid  80  for use of close (operation) overcomes the pressure of operating fluid upon the difference of cross-section area between the valve seat  45  and the disc portion  46  of the control valve  40  for use of close (operation), the spring force of the second spring  31 , the spring force of the third spring  51 , and the friction force, thereby moving the plunger  52  for use of close (operation) towards the left-hand direction. The plunger  52  for use of close (operation) and the valve body  41  of the control valve  40  for use of close (operation) move towards the left-hand direction as one body, thereby opening the control valve  40  for use of close (operation). 
     If it is possible to make the difference small in the diameter between the valve seat  45  and the cylindrical portion  46  of the control valve  40  for use of close (operation), the suction force can be small, which is necessary for driving the plunger  52  for use of close (operation). With this, the space  6  within the cylinder  4  is communicated to the supply side, and then both the spaces  6  and  7  are high in pressure. Since the pressure receiving area of the space  7   a  is larger than that of the space  6  by the cross-section area of the connecting rod  5   a , the piston  5  is pushed upwards. The piston  5  and the movable contact  2  begin the closed-circuit operation. 
     When the closed-circuit operation proceeds, the piston  5  goes up to the top dead center, and the movable contact  2  is in contact with the contact  1 . This condition is that shown in  FIG. 1  mentioned above. Since the supply pressure of high pressure is applied onto the plunger  52  for use of close (operation), the plunger  52  for use of close (operation) keeps a position of suction, after cutting off of the current instruction of the solenoid  80  for use of close (operation). With this, the control valve  20  for use of close (operation) keeps the condition of being opened. 
     In the embodiment mentioned above, since the valve body  41  of the control valve  40  for use of close (operation) is so made up that it cannot move if the plunger  52  does not move, then the valve body  41  can move only up to the position of a distance “p” from the bottom of the housing  48 . However, as shown in  FIG. 8 , it is also possible to make up so that it can move to the position of a distance “q” (&lt;“p”), crossing over the distance “p”. In the similar manner to the case of the control valve  20  for use of open (operation), it is sufficient to change the balancing condition between the fluid force and the oil pressure acting upon the valve seat  41 . This can be achieved by decreasing the difference of cross-section area between the valve seat  45  and the disc portion  46 . 
     In this manner, if bringing the moving stroke of the valve body  41  to be longer than that of the plunger  52 , the moving stroke of the plunger  52  can be made short. Thus, it is possible to make the piston  5  operate quickly, or to operate the piston of a large diameter. 
     When completing the closed-circuit operation of the piston  5 , no fluid force exists. The valve body  41  moves toward the right-hand direction due to the spring force of the third spring  51 . And, it is in contact with the projection portion  43  of the plunger  52  for use of close (operation), thereby stopping. The condition where this plunger  52  for use of close (operation) stops the movement thereof is that shown in  FIG. 1  mentioned above. Under the closed-circuit shown in  FIG. 1 , the space  7   a  within the cylinder  4  is communicated with the supply side of high pressure. Into the space  6  within the cylinder  4  is always applied the high pressure. The piston  5  keeps the closed-circuit condition even if a very small leakage occurs in the control valve  20  for use of open (operation). The control valve  20  for use of open (operation) is kept to be closed due to the supply pressure, which acts upon the difference of cross-section between the valve seat  25  and the cylindrical portion  24 . 
     According to the present embodiment, since the control valves are controlled by electromagnetic solenoids, so as to operate the control valve for use of open (operation) and the control valve for use of close (operation), separately, therefore it is possible to prevent two (2) pieces of the control valves from opening at the same time, during the operation of open-circuit or closed-circuit. As a result of this, it is possible to avoid the blow-by of pressure from the supply side of high pressure to the reservoir side of low pressure, thereby obtaining a stable operation of the fluid pressure operating apparatus. Also, since the high pressure is always applied into one space of the cylinder operation chamber, while the other space thereof is communicated to the reservoir of low pressure when opening circuit, or to the supply side of high pressure when closing circuit, therefore it is possible to keep the open-circuit condition or the closed-circuit condition. 
     Other embodiment according to the present invention will be shown in FIG.  9 . This  FIG. 9  corresponds to that shown in  FIG. 1  of the embodiment mentioned above. The present embodiment differs in the position of the driving portion from the embodiment mentioned above. In the embodiment mentioned above, a pair of the driving portions are connected, on the reverse surface side thereof, and are disposed between the control valve  40  for use of close (operation) and the control valve  20  for use of open (operation). According to the present embodiment, the control valve  20  for use of open (operation) and the control valve  40  for use of close (operation) are neighboring with each other, and on an outside of those are provided the driving portions  73  and  74 , respectively. However, since the control valve  20  for use of open (operation) and the control valve  40  for use of close (operation) are neighboring with each other, the projection portion of the plunger  32  for use of open (operation) and the projection portion  43  of the plunger  52  for use of close (operation) are connected through a connection rod  90 . 
     According to the present embodiment, since the plunger  32  for use of open (operation) and the plunger  52  for use of close (operation) move together as one unit, all of the operations in the embodiment mentioned above can be performed in the same manner. Also, since the control valve for use of open (operation) and the control valve for use of close (operation) are disposed within an inside than the driving portions, then it is possible to shorten the pipe length for each of the conduits, thereby obtaining a small-sizing. It is also possible to operate the plunger for use of open (operation) and the plunger for use of close (operation) by hands, directly from an outside thereof, therefore being cope with emergency, such as when cutting of an electric power source, etc. 
     As was mentioned in the above, according to the present invention, the control valves for driving the piston are driven, directly, by means of the solenoids, therefore it is possible to prevent the operating fluid of high pressure from blowing by to low pressure side, thereby enabling to improve reliability of the fluid pressure operating apparatus for the circuit breaker, as well as, the small-sizing thereof. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential feature or characteristics thereof. The present embodiment(s) is/are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the forgoing description and range of equivalency of the claims are therefore to be embraces therein.