Abstract:
The present invention relates to a safety shutter of a vacuum circuit breaker, and more particularly, to a safety shutter of a vacuum circuit breaker which is mounted on a cradle of a drawable type vacuum circuit breaker and opened or closed when a main body is retracted or pulled out to protect the safety of users from a charging part.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2013-0160480, filed on Dec. 20, 2013, the contents of which are all hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a safety shutter of a vacuum circuit breaker, and more particularly, to a safety shutter of a vacuum circuit breaker which is mounted on a cradle of a drawable type vacuum circuit breaker and opened or closed when a main body is retracted or pulled out to protect the safety of users from a charging part. 
     2. Description of the Conventional Art 
     In general, a vacuum circuit breaker is a circuit breaker installed in a high voltage electric power system to break a circuit to protect the electric power system in the event of a dangerous situation such as a short circuit, an overcurrent, and the like, and it is designed by utilizing excellent insulating performance and arc-extinguishing capability in a vacuum state. 
     The vacuum circuit breaker is categorized into a drawable type vacuum circuit breaker and a fixed type vacuum circuit breaker. That is, the vacuum circuit breaker is divided into a fixed type circuit breaker which consists only of a main body and is fixed to a switch panel, and a drawable type circuit breaker which is configured to have an outer box called a cradle for facilitating the maintenance and repair of the circuit breaker so that a main body is retracted into or pulled out of the cradle. 
       FIG. 1  illustrates a cradle  1  of a drawable type vacuum circuit breaker according to the conventional art. The vacuum circuit breaker includes a variety of auxiliary equipment and safety devices. An example of them is a safety shutter  3  located in front of a charging part  2 . 
     The safety shutter  3  of the vacuum circuit breaker is a device that ensures user safety from the charging part  2  by opening or closing the charging part  2  when a main body (not shown) is retracted or pulled out.  FIG. 2  illustrates the safety shutter (shutter m assembly) of  FIG. 1 . The safety shutter according to the conventional art includes an operating lever  4  that receives the pushing force generated by the forward motion of the main body when the main body is retracted, a shutter guide  5  that moves down by the rotation of the operating lever  4 , a shutter handle  6  that is turned clockwise or counterclockwise by the movement of the shutter guide  5 , a shutter panel  7  that serves to shield the charging part  2 , and shutter link  8  that serves as the axis of rotation while supporting the rotation of the shutter panel  7 . 
     The operation of the safety shutter of the vacuum circuit breaker according to the conventional art will be described as follows. 
     When the main body is retracted into the cradle  1 , a protrusion  4   a  to be brought into contact with the main body is pushed by contact pressure and rotates the operating lever  4  counterclockwise around the coupling axis  4   b.  The shutter guide  5  connected to the front end of the operating lever  4  moves down, and the shutter guide  5  causes the shutter handle  6  rotatably fixed to a cradle side plate  9  by a shutter handle shaft  6   a  to rotate. As the shutter handle  6  rotates, the shutter panel  7  rotates to open the charging part  2 . 
     Hereupon, the shutter panel  7  rotates, supported on the shutter link  8 . That is, the shutter link  8  acts as the axis of rotation, with one end  8   a  attached to the cradle side plates  9 , and the shutter panel  7  is attached to the other end  8   b.  Accordingly, the shutter link  8  has a rotation radius setting when the shutter panel  7  attached to the shutter panel  6  rotates. The radius of rotation is the distance between one end  8   a  and the other end  8   b  of the link. That is, the rotation of the shutter panel  7  depends on the shutter link  8 . However, since the shutter link  8  is fixed, the shutter panel  7  will not move properly and interfere with the charging part  2  or main circuit terminals of the main body in case of any defects or loosening. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention has been made in an effort to solve the above-mentioned problems and provide a safety shutter of a vacuum circuit breaker which operates stably without interference with peripheral parts and facilitates the adjustment of the radius of rotation, rotation speed, and rotation angle of a shutter panel. 
     To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a safety shutter of a vacuum circuit breaker including: a pair of operating levers that rotates by the contact pressure received from a main body, with one end rotatably attached to lower side plates of a cradle; a pair of shutter guides that is made of a plate material and moves vertically, with the lower end connected to the operating levers; a pair of first shutter handles and a pair of second shutter handles that are rotatably mounted on the cradle and rotate with the movement of the shutter guides; a first shutter panel and a second shutter panel that are fixed to one end of the first and second shutter handles to open or close a charging part of the circuit breaker and have panel holders on either side; and a pair of return springs that raises the shutter guides when the main body is pulled out, with the upper end fixed to part of side plates of the cradle and the lower end attached to part of the operating levers, wherein cam holes are formed on the side plates of the cradle so that the panel holders move along the cam holes when the first shutter panel and the second shutter panel are opened or closed. 
     The safety shutter further includes plate-like cam brackets that are attached to the side plates, the cam brackets including bracket cam holes having the same shape as the cam holes. 
     The cam brackets are detachably attached to the side plates. 
     Fastening holes are formed in the side plates, and the cam brackets are attached to the fastening holes. 
     Rollers are attached to the shafts of the panel holders to cause the panel holders to roll along the cam holes when the shutter panels are opened or closed. 
     The radius of rotation, rotation speed, and rotation angle of the first and second shutter panels are adjusted by varying the shape of the cam holes. 
     The first and second shutter panels, the first and second shutter handles, and the cam brackets are symmetrically arranged at upper and lower portions of the cradle so that, when the main body is retracted, the first shutter panel in the upper portion moves upward and the second shutter panel in the lower portion moves downward. 
     A safety shutter of a vacuum circuit breaker according to an embodiment of the present invention is advantageous in that the safety shutter operates stably without interference with peripheral parts. 
     Furthermore, the safety shutter can easily cope with changes in the capacity of the vacuum circuit breaker, the size of the main body, and so on by facilitating the adjustment of the radius of rotation, rotation speed, and rotation angle of the shutter panels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  illustrates a cradle  1  of a drawable type vacuum circuit breaker according to the conventional art; 
         FIG. 2  is a perspective view of a shutter assembly of  FIG. 1 ; 
         FIG. 3  is a perspective view of a cradle of a vacuum circuit breaker according to an embodiment of the present invention; 
         FIG. 4  is a perspective view of a shutter assembly of  FIG. 3 ; 
         FIGS. 5   a  and  5   b  illustrate a top plan view and front view of an operating lever; 
         FIGS. 6   a  and  6   b  illustrate a front view and right side view of a shutter guide; 
         FIGS. 7   a  and  7   b  illustrate a front view and right side view of a shutter handle; 
         FIGS. 8   a  and  8   b  illustrate a front view and left side view of a shutter panel; 
         FIG. 9  is a partial detailed view of a cradle of a vacuum circuit breaker according to another embodiment of the present invention; 
         FIGS. 10  a and  10   b  shows another examples of a cam bracket; and 
         FIG. 11  is a view of the operating state of the shutter assembly, which illustrates the shutter assembly when the main body of the circuit breaker is retracted. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the embodiment will be described for illustrative purposes only so that those skilled in the art can easily work the present invention and does not limit the technical spirit and scope of the invention. 
       FIG. 3  is a perspective view of a cradle of a vacuum circuit breaker according to an embodiment of the present invention.  FIG. 4  is a perspective view of a shutter assembly of  FIG. 3 .  FIGS. 5   a  and  5   b  illustrate a top plan view and front view of an operating lever.  FIGS. 6  a and  6   b  illustrate a front view and right side view of a shutter guide.  FIGS. 7  a and  7   b  illustrate a front view and right side view of a shutter handle.  FIGS. 8  a and  8   b  illustrate a front view and left side view of a shutter panel. The safety shutter of the vacuum circuit breaker according to the embodiment of the present invention will be described in detail with reference to the drawings. 
     A safety shutter of a vacuum circuit breaker according to one embodiment of the present invention includes: a pair of operating levers  20  that rotates by the contact pressure received from a main body, with one end rotatably attached to lower side plates  13  of a cradle  10 ; a pair of shutter guides  30  that is made of a plate material and moves vertically, with the lower end connected to the operating levers  20 ; a pair of first shutter handles  40  and a pair of second shutter handles  46  that are rotatably mounted on the cradle  10  and rotate with the movement of the shutter guides  30 ; a first shutter panel  50  and a second shutter panel  55  that are fixed to one end of the first and second shutter handles  40  and  46  to open or close a charging part  15  of the circuit breaker and have panel holders  51  on either side; and a pair of return springs  60  that raises the shutter guides  30  when the main body is pulled out, with the upper end fixed to part of side plates  11  of the cradle  10  and the lower end attached to part of the operating levers  20 . Cam holes  12  are formed on the side plates  11  of the cradle  10  so that the panel holders  51  move along the cam holes  12  when the first shutter panel  50  and the second shutter panel  55  are opened or closed. 
     The safety shutter, i.e., shutter assembly, of the vacuum circuit breaker according to the embodiment of the present invention roughly includes an operating lever  20 , a shutter guide  30 , shutter handles  40  and  46 , shutter panels  50  and  55 , and a return spring  60 . 
     The operating lever  20  is made up of an L-shaped bar or long panel that forms an obtuse angle. A fastener  21  is provided at one end of the operating lever  20  so as to be rotatably attached to a lower side plate  13  of the cradle  10 . The fastener  21  has a through-hole to attach the operating lever  20  to the lower side plate  13  by a bolt or rivet. The operating lever  20  is rotatable around the fastener  21 . 
     A stopping piece  22  protrudes inward at a bent portion of the operating lever  20 . When the main body (not shown) is retracted, the main body comes into contact with the stopping piece  22  to transfer a forward pushing force and therefore produce torque on the operating lever  20  to cause the operating lever  20  to rotate around the fastener  21 . 
     A sliding hole  23  is longitudinally formed at the other end of the operating lever  20 . The operating lever  20  is connected to the shutter guide  30  to be described later through the sliding hole  23 . 
     The operating lever  20  is provided in a symmetrical pair on the left and right sides of the cradle  10 . 
     The shutter guide  30  is made up of a vertical longitudinal plate. A protrusion  31  is formed on the lower end of the shutter guide  30  and slidably attached to the sliding hole  23  of the operating lever  20 . 
     A first long hole  32  and a second long hole  33  are formed lengthwise on upper and lower parts of the shutter guide  30 . The shutter handles  40  and  46  to be described later are attached to a lower plate  11  of the cradle  10  through the first and second long holes  32  and  33 . As the shutter guide  30  is constrained by a fastening means  45  for attaching the shutter handle  40  to the side plate  11  of the cradle  10 , it moves only vertically. That is, when the operating lever  20  rotates, the protrusion  31  attached to the sliding hole  23  receives force. Because the horizontal component of the force causes sliding, only the vertical component of the force is transferred to the protrusion  31  to move the shutter guide  30  only vertically. 
     A first stopping piece  34  and a second stopping piece  35  are formed inward on the upper and lower parts of the shutter guide  30 , respectively. As viewed in  FIG. 4 , the first stopping piece  34  is formed on the left side of the first long hole  32 , and the second stopping piece  35  is formed on the right side of the second stopping piece  35 . 
     The shutter guide  30  is provided in a symmetrical pair on the left and lower sides of the cradle  10 . 
     The shutter handles  40  and  46  are formed of a rectangular plate material. The shutter handles  40  and  46  consist of a first shutter handle  40  provided at the upper portion of the cradle  10  and a second shutter handle  46  provided at the lower portion of the cradle  10 . A center hole  41  and a plurality of slant holes  42  radially extending from the center hole  41  are formed on one side of the shutter handles  40  and  46 . The shutter handles  40  and  46  are rotatably attached to the side plate  11  of the cradle  10  through the fastening means  45  passing through the center hole  41 . The fastening means  45  may be a bolt or rivet. The shutter assembly is supported by being attached to the side plate  11  of the cradle  10  by the fastening means. 
     The first stopping piece  34  or second stopping piece  35  is inserted into the slant holes  42  of the shutter handles  40  and  46 , and the shutter handles  40  and  46  receive torque by the vertical movement of the shutter guide  30  and rotate clockwise or counterclockwise. That is, as viewed in  FIG. 4 , the downward movement of the shutter guide  30  causes the first shutter handle  40  to rotate counterclockwise because the first stopping piece  34  is attached to a slant hole  42  on the left side of the center hole  41 , and the downward movement of the shutter guide  30  causes the second shutter handle  46  to rotate clockwise because the second stopping piece  35  is attached to a slant hole  42  on the right side of the center hole  41 . 
     A coupling protrusion  43  is formed on the other side of the shutter handle  40  and rotatably attached to the shutter panel  50  to be described later. 
     The shutter handles  40  and  46  are provided in symmetrical pairs on the left and right sides of the cradle  10 . 
     The shutter panels  50  and  55  are approximately rectangular. Panel holders  51  are provided on either side of the shutter panels  50  and  55 . The panel holders  51  are fit to the cam holes  12  of the side plates  11  of the cradle  10 . Although not shown, rollers may be inserted into the shafts of the panel holders  51 . Accordingly, as the panel holders  51  slide along the cam holes  12 , they may roll and move smoothly. Besides, bearings or other parts may be used to help reduce friction. 
     The shutter panels  50  and  55  consist of a first shutter panel  50  provided at the upper portion of the cradle  10  and a second shutter panel  55  provided at the lower portion of the cradle  10 . 
     The upper end of the return spring  60  is fixed to part of the side plate  11  of the cradle  10 , and the lower end thereof is fixed to the center of the operating lever  20 . Normally, the return spring  60  supplies force to maintain the operating lever  20  in a horizontal position. On the other hand, when the main body is pulled out after the shutter guide  30  has moved down by the rotation of the operating lever  20 , the return spring  60  supplies force to pull up the operating lever  20  again. 
     Cam brackets  70  are fastened to positions on the side plates  11  of the cradle  10  where the cam holes  12  are formed. Bracket cam holes  72  are formed in the same shape as the cam holes  12  formed on the side plates  11  of the cradle  10 . According to embodiments, the cam brackets  70  may be detachably fastened to the side plates  11 . That is, referring to  FIG. 9 , a fastening hole  14  of a size enough to include the bracket cam hole  72  is formed in the side plate  11 , and the cam bracket  70  is detachably attached to the side plate  11 . 
     As the cam bracket  70  with the bracket cam hole  72  that comes in a variety of shapes as necessary is fastened to the side plate  11 , the adjustment of the radius of rotation, rotation angle, etc of the shutter panel  50  is facilitated. That is, referring to  FIGS. 10   a  and  10   b , the line of movement of the coupling protrusion  43  of the shutter handle  40  is indicated in virtual line. The bracket cam hole  72   b  of  FIG. 10   b  shows an abrupt change in angle compared to the bracket cam hole  72   a  of  FIG. 10   a , and the rotation speed of the shutter panel  50  therefore changes abruptly. Also, the radius of rotation or the angle of opening or closing the shutter panel  50  can be adjusted by adjusting the start and end positions of the bracket cam hole  72 . 
     The operation of the safety shutter of the vacuum circuit breaker according to the embodiment of the present invention will be described.  FIG. 4  illustrates the shutter assembly when the main body of the circuit breaker is pulled out.  FIG. 11  illustrates the shutter assembly when the main body of the circuit breaker is retracted. 
     When the main body is retracted into the cradle  10 , the operating lever  20  rotates around the fastener  21  by the contact pressure applied on the stopping piece  22 . As the operating lever  20  rotates, the shutter guide  30  connected to the sliding hole  23  moves down. As the shutter guide  30  moves down, the contact pressure received from the first stopping piece  34  or second stopping piece  35  causes the first shutter handle  40  to rotate counterclockwise and the second shutter handle  46  to rotate clockwise. Accordingly, the first shutter panel  50  opens upward and the second shutter panel  55  opens downward. The rotation speed or rotation angle of the shutter panels  50  and  55  is adjusted depending on the shape of the cam holes  72  of the cam brackets  70 . 
     When the main body is pulled out of the cradle  10 , the operating lever  20  rotates clockwise by the restorative force of the return spring  60  applies force in a direction opposite to when the shutter panels  50  and  55  are opened, thereby closing the shutter panels  50  and  55 . 
     It will also be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.