Abstract:
A shutter device is provided for a bypass isolation automatic transfer switch. The shutter device comprises a frame and a shutter that is movably supported by the frame and that is configured to selectively cover and uncover conductors. At least one cam is movably supported by the frame and at least one shutter lever is interposed between the shutter and the at least one cam. The shutter lever is configured to move the shutter in response to movement of the cam.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject matter described herein relates generally to switches and, more particularly, to switches for sourcing electrical energy. 
     2. Related Art 
     Electrical switches for switching a source of electrical energy are known. For example, automatic transfer switches function to switch a main source of power that is reduced or cut off to another source of power. One particular automatic transfer switch is a bypass isolation automatic transfer switch that has an additional feature for preventing non-main source energy from leaking back into the main source. 
     Starting in the mid 1980s and onward, bypass isolation automatic transfer switches have been widely used in the power industry. As the need for critical power installations continues to grow and as power sensitive equipment continues to be developed and installed in locations throughout the U.S. and the world, it continues to become more apparent how important power dependency has become. Current bypass isolation automatic transfer switches have a “top-down” structure that includes an isolation panel affixed to a frame and disposed above an automatic transfer switch. Connection between the isolation panel and the automatic transfer switch is accomplished through movement of the two in a vertical direction. 
     Though highly effective for the given cost, bypass isolation automatic transfer switches have a disadvantage in that the “top-down” structure leads to an enhanced equipment footprint that, in turn, keeps it from being a more popular choice in the market. With the upgrade of power to existing installations, these large bypass units are sometimes too big to fit through existing doorways thus forcing contractors to perform demolition and repair activities on doorways and entry halls. 
     Accordingly, to date, no suitable switch is available which overcomes the above and other disadvantages of the prior art. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with an embodiment of the present invention, a shutter device is provided for a bypass isolation automatic transfer switch. The shutter device comprises a frame, a shutter that is movably supported by the frame and that is configured to selectively cover and uncover conductors. At least one cam is movably supported by the frame and at least one shutter lever is interposed between the shutter and the at least one cam. The shutter lever is configured to move the shutter in response to movement of the cam. 
     In another aspect of the present invention, a method of connecting an automatic transfer switch to a shuttered bypass panel comprises providing a movable automatic transfer switch; fixing a bypass panel to a frame; shuttering receptacles of the bypass panel in response to movement of the automatic transfer switch; and moving the automatic transfer switch to connect the automatic transfer switch to the bypass panel. 
     In a further aspect of the invention, a bypass isolation automatic transfer switch comprises a frame, a bypass panel supported by the frame, a movable automatic transfer switch and a shutter device supported by the frame. The shutter device comprises a frame, a shutter that is movably supported by the frame and that is configured to selectively cover and uncover conductors. At least one cam is movably supported by the frame and at least one shutter lever is interposed between the shutter and the at least one cam. The shutter lever is configured to move the shutter in response to movement of the cam. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description is made with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a switch comprising a frame, an isolation panel and an automatic transfer switch in accordance with one embodiment of the present invention; 
         FIG. 2  is an enlarged, perspective view showing one side of the isolation panel of  FIG. 1 ; 
         FIG. 3  is another enlarged, perspective view showing another side of the isolation panel of  FIG. 1 ; 
         FIG. 4  is an enlarged, perspective view showing one side of the automatic transfer switch of  FIG. 1 ; 
         FIG. 5  is another enlarged, perspective view showing another side of the automatic transfer switch of  FIG. 1 ; 
         FIG. 6  is a perspective view of a portion of the switch of  FIG. 1  showing a shutter shield and a cart for supporting the automatic transfer switch which is omitted; 
         FIG. 7  is another perspective view of a portion of the switch of  FIG. 1  showing a shutter, a shutter lever and a pusher cam in an open position; 
         FIG. 8  is an enlarged view, in perspective, of the shutter lever and the pusher cam of  FIG. 7 ; 
         FIG. 9  is a further enlarged view, from a side, of the shutter lever of  FIG. 7  in a first position; 
         FIG. 10  is another view, similar to that of  FIG. 9 , with the shutter lever in a second position; 
         FIG. 11  is a further enlarged view, from a side, of the pusher cam of  FIG. 7 ; 
         FIG. 12  is another perspective view of the switch of  FIG. 1  showing the shutter in the open position; 
         FIG. 13  is a further perspective view of the switch of  FIG. 1  showing the shutter in the closed position; and 
         FIG. 14  is an enlarged view of a portion of the switch of  FIG. 1  showing automatic transfer switch bus bars adjacent an open window of the shutter. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     One embodiment of the present invention concerns a switch that includes dimensions of both reduced height and depth thus yielding a smaller more compact package for easier installation and use while also providing an enhanced safety feature for the switch. In one particular embodiment, a shutter is provided for covering bus bars of an isolation panel when not connected to bus bars of an automatic transfer switch. 
     Referring now to  FIG. 1 , a switch in accordance with one embodiment of the present invention is illustrated generally at  10 . In this embodiment, the switch  10  comprises a frame  12 , a bypass panel  14 , a movable automatic transfer switch  16 , a racking mechanism  18  for moving the automatic transfer switch  16  into contact with the bypass panel  14  and a shutter mechanism  20 . 
     The frame  12  may comprise any suitably strong and durable sheet material such as a steel or aluminum and may comprise a base  22 , two pairs of upright portions  24  and  26  extending from the base and stabilizing members  28  and  30  interconnected with the upright portions. As shown, each of the base  22 , upright portions  24  and  26  and stabilizing members  28  may comprise appropriate cross-sectional configurations for enhanced strength to support, e.g., the bypass panel  14 , the racking mechanism  18 , and the shutter mechanism  20 . 
     Referring now to  FIGS. 2 and 3 , and  5 , the bypass panel  14  comprises baskets or receptacles  32 ,  34  and  36  that are connectable with blade connectors  50 ,  52 , and  54  ( FIG. 5 ) and are in an exemplary four-pole configuration. In the shown configuration, bus bars  38  and  42  provide power while bus bar  40  provides line return via receptacles  32 ,  34 , and  36  when connected. Mounting plates  44  function to support the bypass panel  14  when fastened to the frame  12 . 
     The automatic transfer switch  16  is best seen in  FIGS. 4 and 5  and comprises blade connectors  50 ,  52  and  54 . The blade connectors  50 ,  52  and  54  are arranged to mate with the receptacles  32 ,  34  and  36  of the bypass panel  14  ( FIG. 2 ) when not covered by the shutter mechanism  20  ( FIG. 1 ) as described in more detail below. 
     Referring again to  FIG. 1 , the automatic transfer switch  16  is mounted to, and supported by, a movable cart  62  that includes handles  64 , support structure  66  and wheels  68 . The handles  64  are provided so that an operator may move the automatic transfer switch  16 , where necessary. 
     The racking mechanism  18  is provided for moving the cart  62  and, in turn, the automatic transfer switch  16 , e.g., for a scheduled maintenance. Upon completion of maintenance, the blade connectors  50 ,  52  and  54  of the automatic transfer switch may be urged together with the receptacles  32 ,  34  and  36  by the racking mechanism  18 . 
     Referring now to  FIGS. 6 and 7 , the shutter mechanism  20  may be connected to the frame  12  and comprises a mounting frame  70 , a shutter shield  72 , a shutter  74 , pusher cams  76  and shutter levers  78 . The mounting frame  70  comprises any suitably strong and durable material such as a steel and may be connected with the frame  12  via suitable fasteners  80  and mounting brackets  82 . Support strips  84  may support a central open portion of the mounting frame  70  as described below. 
     The shutter shield  72  functions to protect the end user against incidental or accidental contact with live parts or the bus systems  32 ,  34 , and  36  and comprises an insulative material such as a polycarbonate or a compressed and treated fiber board. Apertures  86  extend through the shutter shield  72  at appropriate locations to provide for passage of the blade connectors  50 ,  52  and  54  for connection with the receptacles  32 ,  34  and  36 . Mounting slides  88  and  90  may extend along and generally parallel to opposing end portions  92  and  94  of one side (not numbered) of the shutter shield  72 . 
     The shutter  74  may comprise a generally thin sheet of insulative material such as a polymeric substance and, as illustrated, is slidably supported by the mounting slides  88  and  90 . The shutter  74  may comprise apertures  96  and slots  98 . Fasteners  100  may extend through the slots  98  for engagement with the shutter shield  72  and to provide for support and sliding movement of the shutter  74 . 
     Referring now also to  FIG. 8 , in the exemplary embodiment, two pusher cams  76  are illustrated and each may comprise a plate  102  that may comprise mounting slots  104  and a cam surface  106 . The plate  102  may comprise any suitably strong material such as a steel and is configured to be engaged by strike plates  108  of the cart  62 . Fasteners  110 , extend through mounting slots  104 , and stops  112  may be provided for closing reciprocal movement of the pusher cams  76 . The pusher cams  76  extend through apertures  114  in the mounting frame  70  and the shutter shield  72  with the cam surface  106  disposed adjacent the shutter lever  78 . 
     The cam surface  106  (also seen in  FIG. 11 ) may be angled at an angle A that is acute and, in one optional embodiment, angle A may be in the range of between about 38° degrees to about 42° degrees. In one particular embodiment, angle A is approximately 40°. The cam surface  106  functions to urge the shutter lever  78  upon movement of the pusher cam  76 , as described in more detail below. 
     The shutter levers  78  may be disposed in opposing directions or in a mirrored manner as illustrated and each may comprise a strong metallic substance such as a steel. Each shutter lever  78  is rotatable about a pivot portion  115  and each comprises a lever arm  116  and a roller arm  118 . 
     The pivot portion  115  may be pinned by a fastener  120  and a bearing  122  to provide for rotational movement in the direction of arrow  124 . A spring  126  may be provided to bias the shutter lever in one direction that, in turn, biases the shutter  74  in a “closed position”. A couple  128  and stiffening member  130  may be interposed between the shutter lever  78  and the shutter  74 . 
     The lever arm  116  may be rotatably connected to the couple  128  via a bearing  132  and a fastener  134 . 
     The roller arm  118  may extend from the lever arm  116  and may comprise a support bracket  136  that, in turn, comprises members  138  and a roller  140 . The roller  140  may extend through apertures (not numbered) in the members  138  that support bearings  142 . The roller  140  is biased by spring  82  against the cam surface  106 . 
     As shown in  FIGS. 9 through 11 , linear movement of the pusher cam  76  causes movement of the roller  140  along cam surface  106  and, in turn, rotation of the lever arm  116  in the directions of arrows  144  and  146 . The rotation of lever arm  116  may be on the order of between approximately −12° in a clockwise direction and approximately +4° in a counterclockwise direction for a total of about 16° of angular rotation. Rotation of the lever arm  116  causes reciprocal movement of the shutter  72  as illustrated by an arrow  147  in  FIG. 7 . 
       FIGS. 12 and 13  illustrate a racked in position and a racked out position of the automatic transfer switch  16 . Upon movement of the automatic transfer switch  16  in the direction of arrow  148 , blade connectors  50  will be separated from the receptacles  32  ( FIG. 14 ) and the shutter  72  will close. 
       FIG. 14  illustrates a position of the automatic transfer switch  16  just after the shutter  72  has reciprocated out of the way revealing the receptacles  32 . 
     While the present invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the present invention is not limited to these herein disclosed embodiments. Rather, the present invention is intended to cover all of the various modifications and equivalent arrangements included within the spirit and scope of the appended claims.