Abstract:
An air circuit breaker which includes an interlock apparatus which is capable of controlling translocation accurately by preventing deformation and the bending of a lead bar and by minimizing the tolerance in production by constructing the lead bar as two separated bodies and including a guide means for guiding the movement of the lead bar. The interlock apparatus is installed to a base frame for indicating the position of the breaker body, such as a disconnected position in which the breaker body is totally separated from the cradle, a tesing position for testing the breaker body and a connected position in which the breaker is connected to the cradle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a draw out type air circuit breaker, and in particular to an interlock apparatus for indicating the position in a draw out type air circuit breaker which is capable of indicating accurately a disconnected position, a testing position and a connected position when a breaker is pushed in /pulled out from a cradle. 
     2. Description of the Prior Art 
     Generally, an air circuit breaker is installed between an electrical load and an electrical power source in order to protect the load equipment such as a motor and a converter, etc. and a line from an abnormal current (a short circuit, a ground fault, an excess current) generated in an electric circuit such as a power transmission/distribution line and private electricity generating facilities, etc., it means a breaker using air as a medium is for extinguishing an arc generated while opening/closing of contacts. 
     An air circuit breaker is divided into a fixed type fixedly installed between power source and a load and a drawer type in which a breaker is movable so as to be separated from power source and a load in order to facilitate maintenance and secure stability. 
     FIG. 1 is a side view illustrating a state in which a cradle is separated from a breaker body in a general draw out type air circuit breaker. 
     The general draw out type air circuit breaker includes a cradle  100  having an opened side and installed a power source connection terminal  60  connected to power source and a load connection terminal  62  connected to a electrical load equipment, a breaker body  200  movable so as to be pushed in or pulled out from the cradle  100  and performing a circuit cut-off operation in an abnormal current occurrence, and an interlock apparatus  300  for indicating a position of the breaker body  200  by being interlocked with a translocation of the breaker body  200  when the breaker body  200  is pushed in or pulled out from the cradle  100 . 
     Herein, connectors  64 ,  66  are respectively connected to the power connection terminal  60  and the load connection terminal  62  of the cradle  100 , the connectors  64 ,  66  are respectively inserted into a power source connection terminal  68  and a load connection terminal  70  projected from the breaker body  200  and are electrically connected. 
     And, the cradle  100  includes a guide rod  72  for guiding the translocation of the breaker body  200  when the breaker body  200  is pushed in/pulled out. 
     FIG. 2 is a side view illustrating an interlock apparatus of a drawer type air circuit breaker in accordance with the prior art, and FIG. 3 is a front view illustrating the interlock apparatus of FIG. 2 viewing from the right side. 
     The interlock apparatus in accordance with the prior art includes a base frame  102  fixed to the breaker body  200 , shown in FIG. 1, a lead screw  104  supported by the base frame  102  so as to be rotatable, a screw pipe  106  fixed to the cradle  100  and be inserted by the lead screw  104 , an interlock apparatus  300  installed on the base frame  102  and for indicating a position of the breaker body  200  when the lead screw  104  is meshed with the screw pipe  106 , and a locking device  110  connected to the interlock apparatus  300  and locking a position when the breaker body  200  is placed at a disconnected position, a testing position and a connected position. 
     The interlock apparatus  300  includes a lead bar  112  disposed in parallel with the lead screw  104 , contactable to one wall surface of the cradle  100  and retreating relatively when the lead screw  104  is meshed with the screw pipe  106  and linearly moves, a cam  114  connected to the lead bar  112  and installed in the base frame  102  so as to be rotatable for transforming a horizontal linear movement from the retreating lead bar  112  into rotating movement, and a indicating means  150  connected to the side of the cam  114  and for indicating a position of the breaker body  200  in accordance with the rotation of the cam  114 . 
     The lead bar  112  is constructed in one body, one portion of the lead bar  112  is extended in parallel with the lead screw  104 , the other portion of the lead bar  112  is constructed as a curved rod shaped member having a predetermined length so as to be inserted into a slot  118  provided in the cam  114 . 
     And, a breakaway preventing member  120  for preventing a breakaway of the lead bar  112  from the slot  118  is installed to the end of the lead bar  112  inserted into the slot  118 . And, a return spring  122  for providing an elastic force on the lead bar returning to an original position after operation is installed between the breakaway preventing member  120  and the base frame  102 . 
     The cam  114  has a hinge portion  126  so as to be rotatably installed on the base frame  102 , a slot  118  in which the lead bar  112  is inserted is formed at the lower portion of the cam  114  so as to be curved a certain times at a predetermined angle, and a connection pin  124  connected to an indicating plate  116  placed at the front of the hinge portion  126 . 
     As depicted in FIGS. 2 and 3, the indicating means  150  includes the indicating plate  116  linearly moving up or down when the cam  114  rotates by being inserted by the connection pin  124  installed to the cam  114  and having a color indicating portion (not shown) on the upper front surface for indicating a position of the breaker body  200  with colors. A front plate  130  is fixedly installed to the base frame  102  at the front of the indicating plate  116  and having three indicating windows  138 ,  140 ,  142  for respectively indicating a position (a disconnected position, a test position, a connected position) of the color indicating portion of the indicate plate, a handle insertion hole  134  in which a handle (not shown) for rotating the lead screw  104  is inserted at the center portion. A guide plate  132  placed at the rear of the indicating plate  116  and for guiding the up or down movement of the indicating plate  116 . 
     FIGS. 4 and 5 are state diagrams illustrating an operation state of a main parts of an interlock apparatus in accordance with the prior art. 
     In an interlock apparatus of a air circuit breaker in accordance with the prior art, in order to connect the cradle  100  to the breaker body  200 , the breaker body  200  is placed on a guide rod  72  of the cradle  100  and is pushed in, accordingly the breaker body  200  is moved into the cradle  100 . When the lead screw  104  contacts to the screw pipe  106  according to the moving of the breaker body  200  and a user rotates the lead screw  104  by using the handle, the lead screw proceeds into the screw pipe  106  while rotating. 
     Then, the two connection terminals  68 ,  70  projected from the breaker body  200  are connected to the two connectors  64 ,  66  installed to the cradle  100 , accordingly the power source terminal  60  and the load terminal  62  are connected. 
     When the lead screw  104  proceeds, the lead bar  112  contacts to one wall surface of the cradle  100 , herein the lead bar  112  moves in a direction opposite to the lead screw  104 . As described above, when the lead bar  112  retreats, it rotates the cam  114  in the counter-clock wise while moving along the slot  118  of the cam  114 , by the rotation of the cam  114  the indicate plate  116  moves up. Herein, the indicating portion  40  provided on the indicating plate  116  is displayed one of the three indicating windows  138 ,  140 ,  142  of the front plate  130  in order to indicate a present position of the breaker body  200 . 
     In more detail, when the two connection terminals  68 ,  70  projected from the breaker body  200  and the connectors  64 ,  66  installed to the cradle  100  are not connected each other, the circuit is in the cut-off state, at the same time the lead screw  112  is totally separated from the screw pipe  106 , the indicating portion  40  of the indicating plate  116  is displayed on the lowest indicating window  138  of the three indicating windows. Accordingly, the user recognizes the preset position as a disconnected position. 
     And, the lead screw  104  proceeds with a predetermined distance, the cradle  100  and the breaker body  200  are connected each other electrically and mechanically, when an electrical connection between the cradle  100  and the main electrical power source (high voltage power source supplied to the actual circuit between the power source and the load) is cut-off, control electrical power (low voltage power such as AC 110 volt for testing the breaker) is applied to the terminal  60 , when the breaker body  200  reaches the testing position in which a user checks and tests each part of the breaker, the indicating plate  116  moves upwardly with a predetermined distance, the indicating portion  40  is displayed on the middle indicating window  140  of the three display windows, accordingly the user recognizes the breaker body  200  is at the testing position. When the lead screw  104  proceeds completely, the connection terminals  68 ,  70  are inserted into the connectors  64 ,  66  installed to the cradle  100  and reaches the connected position in which main electrical power source is supplied to the circuit between the power source and the load, the indicating portion  40  is displayed on the upper indicating window  142 , accordingly the user recognizes the breaker body  200  is at the connected position. 
     However, in the interlock apparatus of the air circuit breaker in accordance with the prior art, the lead bar for rotating the cam is provided in one body as a rod having a predetermined length and there is no additional guide member for supporting and guiding the movement of the lead bar, so it is easy for the lead bar to be deformed or bent and a translocation of the indicating plate becomes inaccurate, accordingly it is impossible to indicate an accurate position of the breaker body. 
     In addition, there is a predetermined tolerance in order to facilitate the operation and the assembly of the lead bar, the tolerance is increased in accordance with the time passing, accordingly it is impossible to control a translocation accurately. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above-mentioned problems, it is an object of the present invention to provide an air circuit breaker having an interlock apparatus which is capable of controlling a translocation accurately by preventing a deformation and a bent of a lead bar and minimizing a tolerance in production by constructing the lead bar as two separated bars and having a guide means guiding movement of the lead bar. 
     In order to achieve the above-mentioned object, in an air circuit breaker comprising a movable breaker body having a power source terminal and a load terminal and connecting or disconnecting a circuit between power source and a load; 
     a cradle electrically and mechanically connected to or separated from the breaker body in accordance with movement of the breaker body and having a connector electrically and mechanically connected to the breaker body, a screw pipe for guiding the connected to or separated from the breaker body and a power source terminal and a load terminal respectively connected to an electrical power source and an electrical load; 
     a base frame fixed to the breaker body; 
     a lead screw supported by the base frame so as to be rotatable and movable to a position for being inserted into the screw pipe and a position for being separated from the screw pipe; 
     a interlock apparatus installed on the base frame and for indicating a position of the breaker body such as a disconnected position in which the breaker body is totally separated from the cradle, a testing position for testing the breaker body and a connected position in which the breaker body is connected to the cradle; 
     the interlock device comprising; 
     a first lead bar extended from the base frame toward the front end of the lead screw in parallel with the lead screw and for generating a dynamic power for indicating a position of the breaker body by moving in a direction opposite to a forward direction of the lead screw when the lead screw is inserted into the screw pipe; 
     a guide member installed so as to be movable on the lead screw in the base frame, connected to the first lead bar and performing a horizontal linear movement corresponded to the movement of the first lead bar; 
     a second lead bar constructed separately from the first lead bar, connected to the guide member inside the base frame and performing a horizontal linear movement corresponded to the movement of the guide member; 
     a spring installed on the lead screw inside the base frame and for applying an elastic force on the first lead bar in a forward direction of the lead screw; 
     a cam connected to the second lead bar and for transforming the linear movement of the second lead bar into rotating movement; and 
     an indicating means connected to the cam and for indicating a position of the breaker. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view illustrating a general air circuit breaker; 
     FIG. 2 is a side view illustrating an interlock apparatus of an air circuit breaker in accordance with the prior art; 
     FIG. 3 is a front view illustrating the interlock apparatus of FIG. 2 viewing from the right side; 
     FIGS. 4 and 5 are state diagrams illustrating an operation state of a main parts of an interlock apparatus of the air circuit breaker in accordance with the prior art; 
     FIG. 6 is a side view illustrating an interlock apparatus of an air circuit breaker in accordance with the present invention; 
     FIG. 7 is a side view illustrating a lead bar and a guide member of the interlock apparatus in accordance with the present invention; 
     FIG. 8 is a front view illustrating a lead bar and a guide member of the interlock apparatus in accordance with the present invention 
     FIG. 9 is a perspective view illustrating an indicating means of the interlock apparatus in accordance with the present invention; and 
     FIGS. 10 and 11 are state diagrams illustrating an operation state of the interlock apparatus of the air circuit breaker in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of an air circuit breaker in accordance with the present invention will be described with reference to accompanying drawings. 
     There can be a plurality of embodiments of an interlock apparatus of an air circuit breaker in accordance with present invention, hereinafter the most preferred embodiment of the present invention will be described with reference to accompanying FIG.  6 . 
     An air circuit breaker in accordance with the present invention includes a breaker body  200  having an electrical power source terminal and an electrical load terminal, movable, connecting or disconnecting a circuit between an electrical power source and an electrical load, a cradle  100  electrically and mechanically connected to or separated from the breaker body  200  in accordance with movement of the breaker body  200  and having connectors  64 ,  66  for electrically and mechanically connecting to the breaker body  200 , a screw pipe  6  for guiding the connection to or the separation from the breaker body  200  and a power source terminal  60  and a load terminal  62  respectively connected to the electrical power source and the electrical load, a base frame  2  fixed to the breaker body, a lead screw  4  supported by the base frame  2  so as to be rotatable and movable to a position for being inserted into the screw pipe  6  and a position for being separated from the screw pipe  6 , a interlock apparatus  300  installed to the base frame  2  and for indicating a position of the breaker body  200  such as a disconnected position in which the breaker body  200  is totally separated from the cradle  100 , a testing position for testing the breaker body  200  and a connected position in which the breaker body  200  is connected to the cradle  100 . 
     The a interlock apparatus  300  comprises a first lead bar  16  extended from the base frame  2  toward the front end of the lead screw  4  in parallel with the lead screw  4  and for generating a dynamic power in order to indicate a position of the breaker body  200  by moving in a direction opposite to a forward direction of the lead screw  4  when the lead screw  4  is inserted into the screw pipe  106 , a guide member  18  installed so as to be movable on the lead screw  4  inside the base frame  100 , connected to the first lead bar  16  and performing a horizontal linear movement corresponded to the movement of the first lead bar  16 , a second lead bar  20  constructed separately from the first lead bar  16 , connected to the guide member  18  inside the base frame  100  and performing a horizontal linear movement corresponded to the movement of the guide member  18 , a spring  26  installed on the lead screw  4  inside the base frame  100  and for applying an elastic force in a forward direction of the lead screw  4 , a cam  22  connected to the second lead bar  20  and rotating according to the linear movement of the second lead bar  20 , and an indicating means  24  connected to the cam  22  and for indicating a position of the breaker body  200  while moving up or down by the rotation motion of the cam  22 . 
     As depicted in FIG. 6, the base frame  2  is constructed with two steel plates having a “L” shape and a “L” shaped front supporting panel  12  connecting the two steel plates with a predetermined distance each other, and two steel plates having a “L” shape are laid on and installed to the lower portion of the breaker body  200 . A rear supporting panel  14  fixedly installed to the rear of the base frame  2  is further included in order to support the rear end portion of the lead screw  4 . 
     Accordingly, the lead screw  4  is supported so as to be rotatable by the front supporting panel  12  and the rear supporting panel  14  of the base frame  2 . A thread is provided on the outer circumference of the front end of the lead screw  4 , the front end of the lead screw  4  is meshed with the screw pipe  6  having a thread on the inner circumference and fixed to the cradle  100 . In more detail, in order to connect the breaker body  200  to the cradle  100 , when the breaker body  200  is pushed in the cradle  100 , a user rotates the lead screw  4  in the clock wise direction by using the handle, the threaded front end portion of the lead screw  4  is meshed with the threaded inner circumference of the screw pipe  6  on the cradle  100 . When the user rotates the lead screw  4  in the counter-clockwise direction by using the handle for testing or disconnecting the breaker body  200 , the threaded front end portion of the lead screw  4  is separated from the screw pipe  6  of the cradle  100 . A locking device  10  is installed to the lower portion of the base frame  2  in order to lock the position of the breaker body  200  when the breaker body  200  is moved to the disconnected position or the testing position or the connected position. The position locking is performed by inserting a lock bolt into a groove formed at the rear end of the lead screw  4  by the elastic force of a spring (not having a reference numeral), and the position locking is released by pushing a slide bar projected from the lower portion of the indicating means  24  in by the user. For more detail construction and operation of the locking device  10 , it can be referred to the Korean patent application No. 2000-2041 (filing date: Jan. 17th, 2000) filed by the assignee of the present invention about the detailed construction and the operation effect. 
     A groove (not shown) having a polygonal section is provided at the rear end of the lead screw  4  placed in the base frame  2  in order to insert the handle. 
     The first lead bar  16  is a bar-shaped member having a predetermined length extended from the base frame  2  toward the cradle  100  so as to be parallel with the front end of the lead screw  4 . One end of the first lead bar  16  is free end, when the free end of the first lead bar  16  is inserted into the screw pipe, it is contacted to one wall surface of the cradle  100  and is pressed by the wall surface, accordingly the first lead bar  16  retreats in a direction opposite to the insertion direction (forward direction) of the lead screw  4 . The other end of the first lead bar  16  is connected to the guide member  18 . 
     As depicted in FIGS. 7 and 8, The center of the guide member  18  is penetrated by the lead screw  4 , the two steel plates performable the horizontal linear movement are connected each other on the outer circumference of the lead screw  4 . In more detail, the guide member  18  penetrated by the lead screw  4  is installed on the outer circumference of the lead screw  4  in the base frame  2  so as to be performable the horizontal linear movement and is connected to the first lead bar  10  and the second lead bar  20  extended in the opposite direction each other viewing from the guide member  18 . The guide member  18  transmits the dynamic power from the first lead bar  16  to the second lead bar  20  and guides the first lead bar  16  and the second lead bar  20  so as to perform the horizontal linear movement accurately. 
     The spring  26  is installed between the guide member  18  and the rear supporting panel  14 , the spring  26  returns the first lead bar  16  to the original position by providing the elastic force on the first lead bar  16  via guide member  18  in the forward direction of the lead screw  4 . 
     In the spring  26  constructed as a coil spring wound around the outer circumference of the lead screw  4 , one end is supported by the surface of the guide member  18 , and the other end is supported by the rear supporting panel  14 . 
     The second lead bar  20  having a predetermined length is connected between the guide member  18  and the cam  22 , when the guide member  18  is linearly moved, it is linearly moved together and rotates the cam  22 . The end of the second lead bar  20  is connected to the guide member  18 , and a guide pin  28  inserted into the slot  22  formed on the cam  22  and moving along the slot  22  is provided on the other end of the second lead bar  20 . 
     A guide bracket  30  is installed in order to prevent a breakaway of the second lead bar  20  and transmit an accurate stroke to the cam  22  when the second lead bar  20  is linearly moved. In more detail, the guide bracket  30  is constructed as a plate member fixed to the lower plate of the base frame  2  and bent at a right angle, the guide bracket  30  includes a through hole penetrated by the second lead bar  20 , accordingly the guide bracket  30  guides the linear movement of the second lead bar  20  by using the trough hole. 
     The cam  22  is installed on a hinge protrusion  32  projected from the one portion of the base frame  2  and rotates, having a predetermined shaped slot  34  provided at the lower portion of the cam  22  in order to be inserted by the movable guide pin  28  of the second lead bar  20 , and having an operation protrusion  38  at the upper portion of the cam  22  connected to the indicate plate  36  of the indicating means  24  for moving the indicating plate  36  up or down. 
     When the guide pin  28  moves along the slot  34  by the linear movement of the second lead bar  20 , the cam  22  rotates, according to it the operation protrusion  38  rotates together, accordingly the indicate plate  36  moves up or down. 
     As depicted in FIG. 9, the indicating means  24  is for indicating a present position of the breaker body  200  to the user by linearly moving up or down while the rotation of the cam  22 , it includes an indicating plate  36  linearly movable up or down and having an indicating portion  40  for indicating a position of the indicating plate  36  with colors, a front plate  48  placed at the front of the indicate plate  36 , exposed on the front surface of the breaker body  200  and having three indicating windows  42 ,  44 ,  46  for seeing through the indicating portion  40 , and a guide plate  52  placed at the rear of the indicate plate  36 , fixed to the base frame  2  and for guiding the up or down movement of the indicating plate  36 . 
     A front plate  48  has a flat plate, it includes a first indicating window  42  for displaying the indicating portion  40  when the breaker body  200  is at the disconnected position, a second indicating window  44  for displaying the indicating portion  40  when the breaker body  200  is at the testing position, and a third indicating window  46  for displaying the indicating portion  40  when the breaker body  200  is the connected position. 
     A reference numeral  50  is a handle insertion hole for inserting the handle. 
     The operation of the interlock apparatus of the air circuit breaker in accordance with the present invention will be described. 
     FIGS. 10 and 11 are state diagrams illustrating an operation state of the interlock apparatus of the air circuit breaker in accordance with the present invention. FIG. 10 illustrates the interlock apparatus when the breaker body is placed at the disconnected position, and FIG. 11 illustrates the interlock apparatus when the breaker body is connected to the cradle. 
     As depicted in FIG. 1, when the breaker body  200  is totally separated from the cradle  100 , namely, at the disconnected position, there is no contact between the wall surface of the cradle  100  and the first lead bar  16 . Then, as depicted in FIG. 9, the guide member  18  is pushed by the elastic force of the spring  26  and is adjacent to the front supporting plate  12  of the base frame  2 , herein the first lead bar  16  proceeds in the insertion direction of the lead screw  4 . When the first lead bar  16  proceeds, the cam  22  rotates in the clockwise direction, the guide pin  28  is placed at the left groove portion of the slot  34 , at the same time the indicating plate  36  descends in the lowest position, the indicating portion  40  is displayed on the first indicating window  42 , and the user recognizes the breaker body  200  is at the disconnected position. And, the interlock apparatus  8  is locked at the disconnected position by the locking device  10 . As depicted in FIG. 1, at the testing position, the breaker body  200  is not totally separated from the cradle  100 , the power source terminal  2  and the load terminal  4  of the cradle  100  and the connection terminals  10 ,  12  of the breaker body  200  are connected each other, and the lead screw  4  is pulled out not completely but a predetermined length from the screw pipe  6 . At the testing position, the guide member  18  is placed at a middle position between a position depicted in FIG. 10 and a position depicted in FIG. 11, the guide pin  28  is placed at the middle portion of the slot  34 , at the same time the indicating plate  36  ascends a predetermined distance, the color portion displaying the testing position of the indicating portion  40  is displayed on the second indicating window  44 , and the user recognizes the present testing position. And, by the locking device  10 , the interlock device  8  is locked at the testing position. 
     In the meantime, the operation to the connected position will be described in more detail. 
     The breaker body  200  is pushed into the cradle  100 , the lead screw  4  is rotated in the clockwise direction by using the handle (not shown), the lead screw  4  rotates, at the same time proceeds and is inserted into the screw pipe  6 . Herein, the first lead bar  16  is pressed by contacting to the wall surface of the cradle  100  and moves in a direction opposite to the insertion direction (the forward direction) of the lead screw  4 . In more detail, the first lead bar  16  overcomes the elastic force of the spring  26  and retreats correspondingly with a stroke of the proceeding lead screw  4  as depicted in FIG.  10 . When the first lead bar  16  retreats, the guide member  18  moves in a direction away from the front supporting plate  12  along the outer circumference of the lead screw  4 , and the second lead bar  20  connected to the guide member  18  also retreats in the direction away from the front supporting plate  12 . By the retreating of the second lead bar  20 , the guide pin  28  goes back along the slot  34  formed at the cam  22 , the cam  22  rotates in the counter clockwise direction by this retreating movement, and the indicating plate  36  moves upwards. Then, in the indicating portion  40  formed at the indicating plate  36 , the color portion displaying the connected position moves upwards and is displayed on the third indicating window  46  formed at the front plate  48 , accordingly the user recognizes the breaker body  200  is at the connected position. And, the interlock apparatus  8  is locked at the connected position by the locking device  10 . 
     Herein, the guide member  18  moves along the outer circumference of the lead screw  4  and supports the first lead bar  16  so as to move linearly. And, the second lead air  20  is supported by the guide member  18  and the guide bracket  30  and linearly moves. 
     A described above, in the linear movement of the lead screw  4 , in the process for transmitting the stroke of the first lead bar  16  to the indicating plate  36  in order to indicating the translocation of the breaker body  200  according to the movement stroke, the guide member  18  guides and supports the linear movement of the first lead bar  16  while moving along the outer circumference of the lead screw  4 , the supported second lead bar  20  is linearly moved to the guide member  18  and the guide bracket  30 , accordingly the accurate stroke is transmitted and the breakaway is prevented. 
     In an interlock apparatus of an air circuit breaker in accordance with the present invention, a lead bar positioned correspondingly to each position (a disconnected position, a testing position, a connected position) of a breaker body is separately constructed as a first lead bar and a second lead bar, a guide member is installed between the first lead bar and the second lead bar for rotating a cam according to the linear movement of the first lead bar, the second lead bar is supported and guided by the guide member and the guide bracket, it is possible to prevent a deformation or a bent of the lead bar due to force applied on the lead bar, a stroke according to a translocation of the breaker body can be accurately transmitted to the indicating plate, accordingly a user can accurately recognize a position of the breaker body.