Patent Publication Number: US-7223928-B2

Title: Switch with improved protection from ice conditions

Description:
This application claims the benefit of U.S. Provisional Application No. 60/637,158 filed on Dec. 20, 2004. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to the field of electrical switches for electrical power transmission and distribution, and more particularly to an arrangement to protect the switch from the deleterious effects of ice formation that inhibits switch operation. 
   2. Description of the Related Art 
   Outdoor electrical switches for the electrical power transmission and distribution field are subject to the deleterious effects of ice formation that can inhibit proper switch operation. These types of switches are tested under various icing conditions to determine whether or not they will operate properly during outdoor use in the field. In some cases, the opening and closing forces during switch operation are determined such as to permit the switch contact to break free from ice formations during the opening and closing operations. 
   While the prior art arrangements may be useful to provide switches with various features to permit operation under ice conditions, it would be desirable to provide enhanced protection from ice formations. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is a principal object of the present invention to provide an arrangement to protect a switch from the deleterious effects of ice formation that inhibits switch operation. It is another object of the present invention to provide an ice shield that protects the current-carrying contact structures and other operative elements of a switch from ice buildups. 
   These and other objects of the present invention are efficiently achieved by the provision of an arrangement to protect an electrical switch from the deleterious effects of ice formation that inhibits switch operation. In a preferred arrangement, an ice shield is provided that protects the current-carrying contact structures and other operative elements of the switch from ice buildups. In one specific arrangement, as the switch is moved from the open position to the closed position, the ice shield moves away from the contact structure of a moving contact of the switch to permit unfettered engagement with a stationary contact structure of the switch. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in conjunction with the accompanying drawing in which: 
       FIG. 1  is a top plan view of an illustrative electrical switch for use with the arrangement of the present invention to protect the switch from ice formation; 
       FIG. 2  is a perspective view of the arrangement of  FIG. 1  illustrated in an open position corresponding to the closed operating position of the switch; 
       FIG. 3  is a plan view of the arrangement of  FIG. 2  illustrating various operating positions of a movable ice shield of the present invention; and 
       FIG. 4  is a front elevational view of the arrangement of  FIG. 2  with the movable ice shield in a closed position corresponding to the open operating position of the switch. 
   

   DETAILED DESCRIPTION 
   The switch  10  of  FIG. 1  is illustrative of one type of switch that is suitable for use with the ice-protection arrangement  12  of the present invention illustrated in more detail in  FIGS. 2–4 . This type of switch is useful in the electrical power distribution field and is of the type sold by S&amp;C Electric Co., Chicago, Ill. and is of the general type shown in U.S. Pat. Nos. 4,126,773, 3,909,570, and 3,647,996. Referring now additionally to  FIGS. 2–4 , the switch  10  includes a moving contact structure  14  with a switch blade  16  arranged to pivot about a pivot point  15 , a stationary contact structure  18  for engagement with a switch-blade contact portion  17  of the switch blade  16 , and an interrupter  20 . 
   The interrupter  20  includes internal interrupting contacts (not shown) that are actuated via an external trigger structure (not shown) during the interrupting stage of the switch operation via a switch-blade cam  22  (best seen in  FIG. 2 ) on the moving contact structure  14  carried by the switch blade  16 . Specifically, on opening of the switch  10  via movement of the switch blade  16  out of engagement with the stationary contact structure  18  and toward the position shown in  FIG. 1 , a shunt current path is established through the interrupter  20  via a connection with the stationary contact structure  18 , through the internal interrupting contact structure to a shunt contact located at  24  in  FIG. 1  on the outside of the interrupter  20 . The shunt current path is completed to the moving contact structure  14  via an auxiliary contact  26  carried by the switch blade  16 . 
   During opening and after the switch blade  16  has moved to the position of  FIG. 1 , the shunt current path through the interrupter  20  is interrupted internally within the interrupter  20  via actuation of the external trigger structure of the interrupter  20  by the switch-blade cam  22 . In this way, interruption of the circuit occurs within the interrupter  20  via the internal interrupting contacts. Further movement during the opening operation moves the switch blade  16  passed the position of  FIG. 1  in the direction  28 . During switch closing operation in the direction  30 , when the switch blade  16  moves through the position of  FIG. 1  to bring the moving contact portion  17  into engagement with the stationary contact structure  18 , the interrupter  20  is closed via actuation of the external trigger structure by the switch-blade cam  22 . The illustrative switch  10  of  FIG. 1  also includes arcing contacts  32  to absorb the brunt of any arcing that may take place during closing of the switch  10 , i.e. the arcing contacts  32  performing a sacrificial function to prevent arcing between the switch-blade contact portion  17  and the stationary contact structure  18 . 
   In accordance with important aspects of the present invention, the ice-protection arrangement  12  ensures that ice formations will not occur on the moving contact structure  14  that could interfere with appropriate closing operation of the switch  10 , i.e. proper mating contact between the switch-blade contact portion  17  and the stationary contact structure  18 . Additionally, the ice-protection arrangement  12  also ensures against ice formation on the switch-blade cam  22  that might interfere with operation of the switch  10 , e.g. external trigger structure (not shown) on the interrupter  20 . Additionally, if the switch  10  includes the arcing contacts  32 , ice formation is also prevented thereon. 
   In a specific embodiment, the ice-protection arrangement  12  includes a shield assembly  50  movably mounted about a pivot point  52  with respect to the switch blade  16 . Specifically, the shield assembly  50  moves relatively to the switch blade  16  during operation of the switch  10  from the position  50 ′ in  FIG. 3  corresponding to the open position of the switch  10  to the position  50 ″ corresponding to the closed position of the switch  10 , an interim position  50 ′″ also being illustrated in  FIG. 3 . The shield assembly  50  includes a cam  54  that interacts with the interrupter  20  at portion  34  to move the shield assembly  50  as shown in  FIG. 1  which corresponds approximately to the interim position  50 ′″ shown in  FIG. 3 , i.e. in  FIG. 1 , the shield assembly  50  has already been moved out of the position  50 ′. Thus, as the shield assembly  50  is moved during switch closing operation to the position  50 ″, the operative engagement components of the moving contact structure  14  may freely engage with the stationary contact structure  18 . For example, as shown in  FIG. 3 and 4 , the shield assembly  50  covers and protects the switch-blade cam  22 , the switch-blade contact portion  17 , and the arcing contacts  32  of the moving contact structure  14 . 
   The shield assembly  50  is biased toward the protective position  50 ′ corresponding to the switch opened position via a torsion spring  56  arranged to operate between the shield assembly  50  and the switch blade  16  and carried by a bolt  58 . Thus, as the switch  10  is opened and moved away from the closed position, the shield assembly  50  moves from the position  50 ″ relative to the switch-blade  16  to the position  50 ′ protecting the components from ice formations. 
   While there have been illustrated and described various embodiments of the present invention, it will be apparent that various changes and modifications will occur to those skilled in the art. Accordingly, it is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the present invention.