Abstract:
A power switchgear includes a circuit breaker including a container filled with an insulating gas, a stationary contact arranged in the container, and a movable contact that makes a movement to make contact with the stationary contact; an operation unit including a biasing member, and opens and closes the circuit breaker; and a linkage unit that transmits an biasing force of the biasing member to the circuit breaker. The linkage unit includes a rotary shaft, a lever including an engaging hole to be engaged with an outer periphery of the rotary shaft, and a pressing member that presses the rotary shaft onto an inner periphery of the engaging hole.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a power switchgear to be installed in a sub station or the like. 
   2. Description of the Related Art 
   A conventional power switchgear (hereinafter, “a switchgear”) such as one disclosed in Japanese Patent Application Laid-open No. 2001-118474 includes an operation unit and a circuit breaker. The operation unit includes an output shaft to transmit a rotary torque generated by a spring as a driving force charged in advance manually or by a motor. The circuit breaker includes a grounding container filled with an insulating gas, and a stationary contact and a movable contact arranged in the grounding container. The movable contact makes a movement to make contact with the stationary contact. The movable contact is connected to linkage units such as links and levers and a rotary shaft on the grounding container side. The operation unit is accommodated in an operation box that is arranged under the grounding container. With this configuration, a rotary torque transmitted from the output shaft is transmitted to the movable contact through the rotary shaft, the linkage members, and the levers. 
   In this circuit breaker, outer peripheries of the output shaft and the rotary shaft and corresponding inner peripheries of cylindrical coupling members are gear-shaped or spline-shaped (hereinafter, “a gear shape”). The output shaft is connected to the rotary shaft via the coupling member to operate in conjunction with the rotary shaft. 
   However, for assemblability, an inner diameter of the coupling member is essentially larger than an outer diameter of the output shaft or the rotary shaft in the switchgear disclosed in Japanese Patent Application Laid-open No. 2001-118474. This causes a clearance between the coupling member and the output shaft or the rotary shaft and leads to delay in mechanical movement or an undesirable rotational angle when rotational motion by the output shaft is transmitted to the rotary shaft. This may adversely affect mechanical properties of the circuit breaker. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to at least partially solve the problems in the conventional technology. 
   According to an aspect of the present invention, there is provided a power switchgear including a circuit breaker that includes a container filled with an insulating gas, a stationary contact arranged in the container, and a movable contact that makes a movement to make contact with the stationary contact; an operation unit that includes a biasing member, and opens and closes the circuit breaker; and a linkage unit that transmits an biasing force of the biasing member to the circuit breaker, the linkage unit including a rotary shaft, a lever that includes an engaging hole to be engaged with an outer periphery of the rotary shaft, and a pressing member that presses the rotary shaft onto an inner periphery of the engaging hole. 
   The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a switchgear according to a first embodiment of the present invention; 
       FIG. 2  is a plan view of part of a linkage unit shown in  FIG. 1 ; 
       FIG. 3  is a cross sectional view of the linkage unit taken along line A-A of  FIG. 2 ; 
       FIG. 4  is a plan view illustrating a state in which a rotary shaft is engaged with a lever according to a second embodiment of the present invention; 
       FIG. 5  is a perspective view for explaining engagement of a columnar member with an end portion of the rotary shaft shown in  FIG. 4 ; 
       FIG. 6  is a perspective view for explaining engagement of a threaded columnar member with an end portion of a rotary shaft having a threaded inner periphery; 
       FIG. 7  is a perspective view of linkage units according to a third embodiment of the present invention; 
       FIG. 8  is a perspective view of a rotary shaft and a coupling member shown in  FIG. 7 , and a ring; and 
       FIG. 9  is a perspective view of linkage units, each of which includes the rotary shaft, the coupling member, and the ring shown in  FIG. 8 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawings. 
     FIG. 1  is a perspective view of a switchgear  100  according to a first embodiment of the present invention. The switchgear  100  includes grounding containers  1 , an operation unit  4 , stationary contacts  2 , movable contacts  3 , pressing elements  5 , levers  6 , rotary shafts  7 , levers  8 , linkage members  9 , an output lever  10 , a cutoff lever  11 , and a spring  12 . 
   The switchgear  100  is configured to open or close a circuit breaker per alternating current phase. For example, the switchgear  100  includes three grounding containers  1  and linkage units corresponding to the respective grounding containers  1  as shown in  FIG. 1 . The linkage units transmit a biasing force of the spring  12  to the movable contacts  3 . Each of the linkage units includes, although not limited, the pressing element  5 , the rotary shaft  7 , the levers  6  and  8 , and the linkage member  9 . In addition, each of the linkage units includes a pressing member for pressing an outer periphery of the rotary shaft  7  against each mating inner periphery of the engaging holes formed in the levers  6  and  8 . 
   The grounding container  1  is filled with an insulating gas. The grounding container  1  functions as a circuit breaker by having the stationary contact  2 , the movable contact  3  arranged opposed to the stationary contact  2 , and the pressing element  5  that moves the movable contact  3  toward and away from the stationary contact  2 . 
   The lever  6  that is arranged inside the grounding container  1  includes a gear-shaped engaging hole with which a gear-shaped outer periphery of the rotary shaft  7  is engaged, so that rotary torque of the rotary shaft  7  is transmitted to the lever  6 . The lever  6  further includes a pivot that pivotally supports the pressing element  5 . With this configuration, the lever  6  swings around the engaging hole, so that a rotational motion of the rotary shaft  7  can be converted into a reciprocating motion of the pressing element  5 . 
   The lever  8  that is arranged outside the grounding container  1  includes a pivot that pivotally supports the linkage member  9  and a gear-shaped engaging hole with which a gear-shaped outer periphery of the rotary shaft  7  is engaged. The lever  8  swings around the engaging hole, so that a reciprocating motion of the linkage member  9  can be converted into a rotational motion of the rotary shaft  7 . The outer periphery of the rotary shaft  7  and the engaging holes of the levers  6  and  8  can be formed into any shape so long as transmission of the rotational torque of the rotary shaft  7  to the levers  6  and  8  is possible. 
   The linkage members  9  connect each of the levers  8  for each phase to the output lever  10  in the operation unit  4 , so that a biasing force of the spring  12  can be transmitted to each of the levers  8 . The cutoff lever  11  is connected to the spring  12  in which a biasing force has been charged in advance manually or by a motor (not shown). The output lever  10  and the cutoff lever  11  are connected to be integrally rotated by a biasing force of the spring  12 . The structures of the output lever  10  and the cutoff lever  11  are the same as those of the levers  6  and  8 , which therefore will not be explained. 
     FIG. 2  is a plan view of part of a linkage unit according to the first embodiment. The rotary shaft  7  has a gear-shaped cross section, and each engaging hole formed in the levers  6  and  8  is formed into a gear shape to be engaged with the rotary shaft  7 . 
   As shown in  FIG. 2 , there is a clearance between the rotary shaft  7  and the engaging hole in each of the levers  6  and  8 . To address this clearance, each of the levers  6  and  8  has a through hole  13  that reaches the rotary shaft  7 . A screw  14  is inserted into the through hole  13  to press the rotary shaft  7  against the engaging hole, whereby the clearance between the rotary shaft  7  and the engaging hole is eliminated. 
     FIG. 3  is a cross sectional view of part of the linkage unit taken along line A-A of  FIG. 2 . As shown in  FIG. 3 , the rotary shaft  7  is engaged with the engaging hole of the lever  8  in the lower portion while the screw  14  is inserted into the through hole  13  formed in the lever  8 . Although not shown in  FIG. 3 , the rotary shaft  7  is engaged with the lever  6  in the upper portion in the same manner. 
   A sealing member  15  having a predetermined thickness is provided around the rotary shaft  7  to prevent gas leakage from the grounding container  1  or air entry into the grounding container  1 . 
   As mentioned above, because each of the levers  6  and  8  has the through hole  13 , the screw  14  inserted into the through hole  13  presses the rotary shaft  7  to shift the central axis of the rotary shaft  7  from a center of the engaging hole. In other words, the linkage unit includes a pressing member to press the outer periphery of the rotary shaft  7  against the inner periphery of each of the engaging holes in the levers  6  and  8 . The screw  14  serves as the pressing member. 
   According to the first embodiment, a clearance at an engaging portion of a shaft and a mating hole is eliminated by pressing the outer periphery of the shaft against the inner periphery of the mating hole, so that rotational angular deviation at each linkage unit can be eliminated. As a result, disadvantageous movements such as operational delay of a lever, insufficient rotation of a rotary shaft, or uncoupled operations of circuit breakers among a plurality of phases that may adversely influence mechanical properties of a switchgear can be eliminated. Furthermore, energy saving and prolonged durability of a switchgear are attainable because of elimination of unintended mechanical movements in the switchgear. 
     FIG. 4  is a plan view illustrating a state in which a rotary shaft  20  is engaged with the lever  6  (or the lever  8 ) according to a second embodiment of the present invention. Other members associated with the rotary shaft.  20  and the levers  6  and  8  are as shown in  FIG. 2 . 
   The rotary shaft  20  is cylindrical and includes a number of axially segmented portions. An outer periphery of the rotary shaft  20  is gear shaped same as that of the rotary shaft  7  in the first embodiment. Moreover, an inner periphery of each of engaging holes in the levers  6  and  8  is gear shaped same as that of the rotary shaft  20 , so that the outer periphery of the rotary shaft  20  is engaged with the inner periphery of the engaging hole in the lever  6  or  8 . 
     FIG. 5  is a perspective view for explaining engagement of a columnar member  21  with an end portion of the rotary shaft  20 . The columnar member  21  can be press-inserted into a hollow portion  22  (shown in  FIG. 4 ) of the rotary shaft  20 . When the columnar member  21  is press-fitted into the hollow portion  22  after the rotary shaft  20  has been inserted into the levers  6  and  8  (both are not shown in  FIG. 5 ), the columnar member  21  presses the end portion of the rotary shaft  20  outwardly. As a result, the outer periphery of the rotary shaft  20  can be made fitted with the inner periphery of each of the engaging holes in the levers  6  and  8 . In other words, the linkage unit includes a pressing member to press an outer periphery of the rotary shaft against a mating inner periphery of the engaging hole formed in each lever. The columnar member  21  serves as the pressing member. 
   The columnar member  21  is not limited to a columnar shape and can be formed into, for example, a tapered shape. The columnar member  21  can be made of an elastic material. When the columnar member  21  is made of an elastic material, the columnar member  21  in a compressed state can be inserted into the hollow portion  22  and expands the rotary shaft  20  outwardly by an expansion force. The rotary shaft  20  can have a tapered inner periphery and axially segmented portions. 
     FIG. 6  is a perspective view for explaining engagement of a columnar member  24  with an end portion of a rotary shaft  23  having a threaded inner periphery. The rotary shaft  23  is cylindrical with a threaded inner periphery and includes a number of axially segmented portions. The columnar member  24  is threaded to be screwed into the rotary shaft  23 . When the columnar member  24  is screwed into the hollow portion  22  after the rotary shaft  23  has been inserted into each of engaging holes in the levers  6  and  8  (both are now shown in  FIG. 6 ), the columnar member  24  presses the end portion of the rotary shaft  23  outwardly. As a result, the outer periphery of the rotary shaft  23  can be made fitted with the inner periphery of the engaging hole. In other words, the linkage unit includes a pressing member to press an outer periphery of the rotary shaft against a mating inner periphery of the engaging hole formed in each lever. The columnar member  24  serves as the pressing member. 
   According to the second embodiment, in addition to the above effects, workability in assembling the linkage units or the like can be improved by using a tapered columnar member. Moreover, use of a threaded tapered columnar member further facilitates the workability and prevents disengagement of the tapered columnar member. 
     FIG. 7  is a perspective view of linkage units according to a third embodiment of the present invention. Each of the linkage units corresponds to the pressing element  5 , the lever  6 , the rotary shaft  7 , the lever  8 , and the linkage member  9  shown in  FIG. 1 . In each of the linkage units shown in  FIG. 7 , either one of the lever  6  or  8 , and the rotary shaft  7  are omitted. In place of the linkage members  9  shown in  FIG. 1 , rotary shafts  34   a,    34   b,  and  34   c,  and coupling members  35   a,    35   b,  and  35   c  are used for interconnecting phases. 
   The linkage unit that includes a pressing element  30   a,  a link  31   a,  and a lever  32   a  transmits a driving force to move the movable contact  3  of phase A shown in the left side in  FIG. 1 . The linkage unit for phase B (shown in the middle in  FIG. 1 ) and the linkage unit for phase C (shown in the right side in  FIG. 1 ) function in the same manner as the linkage unit for phase A. 
   The phases A and B are connected with a linkage rod unit including the rotary shaft  34   a  and the coupling member  35   a,  and the phases B and C are connected with a linkage rod unit including the rotary shaft  34   b  and the coupling member  35   b.  A linkage rod unit including the rotary shaft  34   c  and the coupling member  35   c  (shown in the lower right in  FIG. 7 ) corresponds to an output shaft that is connected to the operation unit  4  shown in  FIG. 1 , and therefore transmits a rotary torque from the operation unit  4  to each phase. The linkage units for the phases A, B, and C are configured to operate in conjunction with one another by the rotary torque. An outer periphery of each of the rotary shafts  34   a,    34   b,  and  34   c,  and an inner periphery of each of engaging holes in the levers  32   a,    32   b,  and  32   c  are gear shaped. 
   As mentioned in the first embodiment, there is a clearance between each of the rotary shafts  34   a,    34   b,  and  34   c  and corresponding each engaging hole in the levers  32   a,    32   b,  and  32   c.  Each of the levers  32   a,    32   b,  and  32   c  has a through hole that reaches corresponding each of the rotary shafts  34   a,    34   b,  and  34   c.  A screw  33  is inserted into the through hole to press the rotary shaft against the engaging hole, whereby the clearance can be eliminated. In other words, the linkage unit includes a pressing member to press an outer periphery of each rotary shaft against a mating inner periphery of the engaging hole formed in each lever. The screw  33  serves as the pressing member that presses each shaft so that each central axis of the rotary shafts is shifted from a center of corresponding each inner periphery of the engaging holes. 
     FIG. 8  is a perspective view of a rotary shaft  34  (corresponding to the rotary shafts  34   a,    34   b,  and  34   c  in  FIG. 7 ) and a coupling member  35  (corresponding to the coupling members  35   a,    35   b,  and  35   c  in  FIG. 7 ) according to the third embodiment of the present invention. 
   The coupling member  35  is cylindrical and axially segmented to be detachable. An inner periphery of the coupling member  35  is gear shaped to be engaged with an outer periphery of the rotary shaft  34 . With this configuration, a driving force from the spring  12  is transmitted to the rotary shaft  34 . 
   The coupling member  35  is surrounded by an annular ring  38 , which is fastened by bolts  36  provided at the ends thereof, whereby the segmented portions of the coupling member  35  are pressed toward a center thereof to fit the rotary shaft  34 . 
     FIG. 9  is a perspective view of linkage units. Rings  38   a,    38   b,  and  38   c  correspond to the ring  38  shown in  FIG. 8 , the coupling members  35   a,    35   b,  and  35   c  correspond to the coupling member  35 , and bolts  36   a,    36   b,  and  36   c  correspond to the bolts  36 . 
   The phases A and B are connected with a linkage rod unit including the rotary shaft  34   a,  the coupling member  35   a,  and the ring  38   a,  and the phases B and C are connected with a linkage rod unit including the rotary shaft  34   b,  the coupling member  35   b,  and the ring  38   b.  A linkage rod unit including the rotary shaft  34   c,  the coupling member  35   c,  and the ring  38   c  corresponds to the output shaft that is connected to the operation unit  4  as shown in  FIG. 1 , and therefore transmits a rotary torque from the operation unit  4  to the linkage units for the phases A, B, and C, whereby the linkage units can operate in conjunction with one another by the rotary torque. 
   According to the third embodiment, in addition to the above effects, a rotary torque from an operation unit can be uniformly transmitted to levers for a plurality of phases. As a result, an adverse effect due to operational fluctuation in circuit breakers among the phases can be eliminated. Furthermore, coupling members are configured to be easily detachable without disassembling all of the linkage units, so that assemblability and workability have can be improved. Moreover, easy angular adjustment of a lever has been realized. 
   According to an aspect of the present invention, a pressing member is provided, so that rotational angular deviation at an engaging portion of a shaft and a mating hole can be suppressed. 
   Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.