Abstract:
An arc chute assembly is for an electrical switching apparatus including a housing and an arc hood coupled thereto, the arc hood being structured to exhaust arc gases from the housing. The arc chute assembly includes a vent portion structured to exhaust arc gases from the housing into the arc hood and a frame portion adjacent the vent portion. The frame portion being structured to be movably coupled to the housing. The arc chute assembly being structured to be movable from a first position to a different second position relative to the housing responsive to the exhaust arc gases.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates generally to electrical switching apparatus and, more particularly, to arc chute assemblies and arc hood assemblies for electrical switching apparatus, such as circuit breakers. 
   2. Background Information 
   Electrical switching apparatus, such as circuit interrupters, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit interrupters, such as circuit breakers, include a housing and an operating mechanism, which opens separable electrical contacts to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit. 
   Some low-voltage circuit breakers, for example, have arc chute vents on a portion (e.g., without limitation, the top) of the housing. When the separable electrical contacts rapidly open, for example, in response to an overload or short circuit condition, an arc is created which generates gases that are expelled from the vents. The gases can be extremely hot, are at least partly ionized, and may carry debris, such as molten metal particles. Furthermore, the gases and debris can be electrically conductive and, therefore, can cause additional undesirable arcing between the circuit breaker and grounded electrically conductive features proximate the circuit breaker, including but not limited to, the metallic enclosure in which such circuit breaker is typically installed. The gases may also be expelled with explosive force and may, therefore, damage components of the enclosure. 
   Accordingly, switchgear enclosures are typically designed to include one or more channels in which arc gases can be directed for dissipation thereof. Some switchgear cabinets also include an insulated barrier, commonly referred to as an arc hood, which is mounted above the arc chute vents of the circuit breaker through which the arc gases are exhausted. The arc hood functions to manage the effects of the arc gases and, in particular, to cool and dissipate the arc gases within the arc hood. However, there is room for improvement in the interface between the arc chute and arc hood. 
   SUMMARY OF THE INVENTION 
   These needs and others are met by embodiments of the invention, which are directed to an arc chute assembly for an electrical switching apparatus, an arc hood assembly for an electrical switching apparatus, and an electrical switching apparatus in which the arc chute assembly comprises a vent portion structured to exhaust arc gases from a housing into an arc hood and a frame portion adjacent the vent portion, with the frame portion structured to be movably coupled to the housing. The arc chute assembly is structured to be movable from a first position to a different second position relative to the housing responsive to the exhaust arc gases. 
   As one aspect of the invention, an arc chute assembly for an electrical switching apparatus is provided. The electrical switching apparatus includes housing and an arc hood coupled thereto. The arc hood being structured to exhaust arc gases from the housing. The arc chute assembly comprises: a vent portion structured to exhaust arc gases from the housing into the arc hood and a frame portion adjacent the vent portion, with the frame portion structured to be movably coupled to the housing. The arc chute assembly is structured to be movable from a first position to a different second position relative to the housing responsive to the exhaust arc gases. 
   The frame portion may be structured to abut the housing when at the first position and may be further structured to be generally spaced from the housing when at the different second position. 
   The arc hood may comprise a number of transverse members and the arc chute assembly may be structured to be spaced from the number of transverse members when at the first position. The arc chute assembly may be further structured to abut the number of transverse members when at the different second position. 
   The frame portion may comprise a number of fasteners structured to slidably couple the frame portion to the housing. The number of fasteners may comprise a shoulder bolt. 
   As another aspect of the invention, an arc hood assembly is for an electrical switching apparatus including a housing having a number of arc chutes with a vent portion structured to exhaust arc gases from the housing and a frame portion adjacent the vent portion. The number of arc chutes being movable from a first position to a different second position during venting of the arc gases. The arc hood assembly comprises: a hood member fixedly coupled to the housing at or near the number of arc chutes, the hood member being structured to receive and exhaust the arc gases vented from the housing, and a number of transverse members structured to contact the number of arc chutes when the number of arc chutes are in the different second position. 
   Each of the number of transverse members may comprise a substantially planar member. The vent portion may be generally planar and the substantially planar member may be oriented generally transverse to the vent portion. The number of transverse members may be structured to be spaced a predetermined distance from the number of arc chutes when the number of arc chutes are in the first position, and the number of transverse members may be structured to abut the number of arc chutes when the number of arc chutes are in the second position. 
   As a further aspect of the invention, an electrical switching apparatus comprises: a housing, separable contacts enclosed by the housing, and an operating mechanism structured to open and close the separable contacts. The separable contacts being structured to create an arc that generates arc gases when the separable contacts open. The electrical switching apparatus further comprises: a number of arc chute assemblies disposed with respect to the housing and an arc hood coupled to the housing at or near the vent portion of each of the number of arc chute assemblies. The arc hood being structured to receive the arc gases exhausted from the vent portion of each of the number of arc chute assemblies and exhausts the arc gases from the electrical switching apparatus. Each of the number of arc chute assemblies comprises: a frame portion movably coupled to the housing and a vent portion adjacent the frame portion, the vent portion being structured to exhaust the arc gases from the housing. Each of the number of arc chute assemblies being structured to be movable from a first position to a different second position relative to the housing responsive to the arc gases which exhaust from the housing. 
   The frame portion may abut the housing when at the first position and the frame portion may be spaced a distance from the housing when at the different second position. 
   The arc hood may comprise a number of transverse members. The number of arc chute assemblies may be spaced a predetermined distance from the number of transverse members when at the first position and the number of arc chute assemblies may abut the number of transverse members when at the different second position. 
   The frame portion may be movably coupled to the housing by a number of fasteners. Each of the number of fasteners may comprise a shoulder bolt. 
   Each of the number of transverse members may comprise a substantially planar member. The vent portion may be generally planar and the substantially planar member may be oriented generally transverse to the vent portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
       FIG. 1  is an isometric view of a circuit breaker and an arc hood assembly therefor, in accordance with an embodiment of the invention, showing the circuit breaker operating mechanism, a pair of separable contacts, and an arc in simplified form; 
       FIG. 2  is a partially exploded isometric view of the circuit breaker and arc hood assembly of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view along lines  3 - 3  of  FIG. 1  showing the arc chute assembly in a first position in accordance with an embodiment of the invention; and 
       FIG. 4  is a cross-sectional view similar to  FIG. 3  except showing the arc chute assembly in a different second position responsive to exiting arc gases. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   For purposes of illustration, embodiments of the invention will be described as applied to low-voltage circuit breakers, although it will become apparent that they could also be applied to a wide variety of electrical switching apparatus (e.g., without limitation, circuit switching devices and other circuit interrupters, such as contactors, motor starters, motor controllers and other load controllers) other than low-voltage circuit breakers and other than low-voltage electrical switching apparatus. 
   Directional phrases used herein, such as, for example, left, right, top, bottom, upper, lower, front, back and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. 
   As employed herein, the term “fastener” shall mean a separate element or a number of elements which is/are employed to connect or tighten two or more components together, and expressly includes, without limitation, rivets, pins, screws, bolts and the combinations of bolts and nuts (e.g., without limitation, lock nuts) and bolts, washers and nuts. 
   As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. 
   As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
     FIGS. 1 and 2  show an electrical switching apparatus such as, for example, a low-voltage circuit breaker  2 , and an arc hood assembly  100  therefor. The circuit breaker  2  includes a housing  4 , separable contacts  6  (shown in simplified form in hidden line drawing in  FIG. 1 ) enclosed by the housing  4 , an operating mechanism  10  (shown in simplified form in hidden line drawing in  FIG. 1 ), which is structured to open and close the separable contacts  6  ( FIG. 1 ), and a number of arc chutes  16  ( FIGS. 2-4 ). 
   The housing  4  of the example circuit breaker  2  includes a first end  22 , a second end  24 , a first side  26 , a second side  28 , a front  30 , and a back  32 . The circuit breaker  2  is disposable within a cassette  170 , which in the example shown and described herein includes a bottom  172  and first and second sides  174 , 176  extending perpendicularly outwardly from the bottom  172 . When the circuit breaker  2  is disposed within the cassette  170 , as shown in  FIGS. 1 and 2 , the first side  26  of the circuit breaker housing  4  is disposed adjacent the first side  174  of the cassette  170 , and the second side  28  of the circuit breaker housing  4  is disposed adjacent the second side  176  of the cassette  170 . Thus, the second end  24  of the circuit breaker housing  4  is disposed adjacent the bottom  172  of the cassette  170 , and the first end  22  of the circuit breaker housing  4  is disposed at or about the ends  178 , 180  of the first and second sides  174 , 176  of the cassette  170 , as shown. 
   As shown in  FIG. 2 , each of the arc chutes  16  includes a frame portion  18  and a vent portion  20  with the frame portion  18  generally surrounding the vent portion  20 . Each of the arc chutes  16  is generally oriented within the circuit breaker  2  such that the respective frame and vent portions  18 , 20  are generally disposed at or near the first end  22  of the housing  4 . Each of the vent portions  20  is structured to exhaust arc gases  14  (shown in phantom line drawing in  FIGS. 2 and 4 ) from the housing  4 . As shown in  FIG. 1 , the arc gases  14  are generated from an arc  12  that is created when the separable contacts  6  open. 
   As shown in  FIGS. 3 and 4 , each of the arc chutes  16  is movably coupled to the housing  4  via a number of shoulder bolts  34  that pass through stepped holes  36  in the frame portion  18  and are securely coupled to the housing  4 . The shoulder bolts  34  allow for each of the arc chutes  16  to move from a first position ( FIG. 3 ), in which the frame portion  18  generally abuts the housing  4 , to a second position ( FIG. 4 ) in which the frame portion  18  is generally spaced from the housing  4  upon passing of the exhaust arc gases  14  through the vent portion  20  of the respective arc chute  16 . Such movement of the arc chutes  16  will be further discussed below. 
   The cassette  170  of  FIGS. 1 and 2  further includes an arc hood assembly  100  generally spanning across the top of the cassette  170  from the end  178  of the first side  174  to the end  180  of the second side  176 . The arc hood assembly  100  is generally positioned to cover the frame and vent portions  18 , 20  of each of the arc chutes  16  when the circuit breaker  2  is fully installed within the cassette  170  and is preferably formed from MAR-BAL MB2000-20, RED-Eaton Specification #80220AA, however other suitable materials may be employed without departing from the scope of the invention. 
   Referring to  FIG. 2 , the arc hood assembly  100  generally includes a first side  102 , a second side  104 , a first end  106 , a second end  108 , and a top  110 . As shown in  FIG. 4 , the arc hood assembly  100  is structured to receive the exhausted arc gases  14  (previously discussed) from the vent portions  20  of each of the arc chutes  16 . In order to further provide for the venting of the arc gases  14  from the circuit breaker  2  and cassette  170 , the arc hood assembly  100  includes a number of apertures  112  through which the exhausted arc gases  14  may further pass, as shown in  FIG. 1 . The example arc hood assembly  100  shown includes two apertures  112 , however it is to be appreciated that any suitable number/and or configuration of apertures  112  could be employed without departing from the scope of the invention. 
   As shown in  FIGS. 3 and 4 , the arc hood assembly  100  further includes a number of cross-members  114  that generally extend between the first and second sides  102 , 104  of the arc hood assembly  100 . Preferably, each of cross-members  114  is of generally planar shape and formed from a standard cold or hot rolled steel Eaton specification #10102HT or #10101AC respectively cut from conventional sheet or roll steel at specified thickness. However, it is to be appreciated that other suitable materials may be employed without departing from the scope of the invention. As shown in  FIG. 3 , each of the cross-members  114  is preferably oriented generally transverse to vent portion  20  and generally spaced a distance D from the vent portion  20  when the arc chute  16  is in the first position. As shown in  FIG. 4 , when the arc chute  16  is moved to a second position due to the passing of exhaust arc gases  14  through the vent portion  20 , the vent portion  20  abuts cross-member  114  such that cross-member  114  effectively limits the upward travel (with respect to  FIGS. 3 and 4 ) of the arc chute  16 . 
   In order to prevent uncontrolled escape of the exhaust arc gases  14 , a flexible gasket  116  is provided that generally seals between the respective frame portions  18  of each of the arc chutes  16  and the arc hood assembly  100 . Preferably, gasket  116  is made of VITON RUBBER DUROMETER 55-65 SHORE A, BLACK Eaton Specification #45551HB1PE, however other suitable materials may be employed without departing from the scope of the invention. The preferred flexibility of the gasket  116  allows for a seal to be maintained between each of the frame portions  18  and the arc hood assembly  100  when the arc chute  16  is disposed in the first position ( FIG. 3 ), the second position ( FIG. 4 ), or at any position there between. 
   While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.