Patent Publication Number: US-2016249467-A1

Title: Pressure relief mechanism for an electrical housing and method

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to the art of electrical housings and, more particularly, to a pressure relief mechanism for an electrical housing and method. 
     Electrical switching and protection components are typically mounted in a housing. For example, an electrical housing may include circuit breaker compartments that support, and protect one or more circuit breakers. Conventional circuit breakers, in addition to providing over current protection, also provide protection during arc fault events. During an arc fault event, gases often develop and expand outwardly from the circuit breaker. The gases are passed into a vent which provides ventilation of the electrical housing. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of an exemplary embodiment, a pressure relief system for an electrical housing includes at least one wall having a first surface defining, at least in part, a compartment, and a second surface defining, at least in part, a ventilation passage. The at least one wall includes an opening fluidically connecting the compartment and the ventilation passage. The pressure relief system includes a closure mounted to the at least one wall at the opening. The closure is selectively moveable between a closed position covering the opening and an open position uncovering the opening and fluidically connecting the compartment and the ventilation passage. A biasing member is coupled to the closure. The biasing member is operative to bias the closure to the closed position and, in response to a pressure wave within the compartment, allow the closure to move to the open position fluidically connecting the compartment and the ventilation passage. The biasing member is further operative to bias the closure to the closed position after at least a portion of the pressure wave has passed from the compartment into the ventilation passage. 
     According to another aspect of an exemplary embodiment, a method of ventilating a circuit breaker compartment in an electrical housing includes opening a pressure relief system in response to a selected peak value of a pressure wave in a compartment of the electrical housing, and closing the pressure relief system after at least a portion of the pressure wave has exhausted from the compartment. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  depicts an electrical housing including a pressure relief system, in accordance with an exemplary embodiment, shown in a closed configuration; 
         FIG. 2  depicts an electrical housing of  FIG. 1  illustrating the pressure relief system in an open configuration; 
         FIG. 3  is an end view of the pressure relief system of  FIG. 1 ; 
         FIG. 4  is an end view of the pressure relief system of  FIG. 2 ; 
         FIG. 5  is a plan view of the pressure relief system, in accordance with an exemplary embodiment; 
         FIG. 6  is an exploded view of the pressure relief system of  FIG. 5 ; and 
         FIG. 7  is a graph depicting an initial opening of the pressure relief system relative to a peak of a pressure wave, in accordance with an exemplary embodiment. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     An electrical housing, in accordance with an exemplary embodiment, is illustrated generally at  2 , in  FIG. 1 . Electrical housing  2  includes a compartment  4  which, in accordance with an aspect of an exemplary embodiment, may be a circuit breaker compartment. Of course, it should be understood that compartment  4  may house other electrical components. Compartment  4  is defined by a first side wall  8 , a second side wall  10 , a third side wall  12 , and a fourth side wall  14 . A ventilation passage  20  may be arranged outwardly of compartment  4 . In the exemplary embodiment shown, ventilation passage  20  is defined between second side wall  10  and another wall  24 . In further accordance with the exemplary embodiment shown, second side wall  10  includes a first surface  26  and an opposing, second surface  28 . An opening  30  extends through the first and second surfaces  26  and  28  fluidically connecting compartment  4  and ventilation passage  20 . 
     In accordance with an exemplary embodiment, electrical housing  2  includes a pressure relief system  40  arranged at opening  30 . Pressure relief system  40  shifts between a normally closed position, such as shown in  FIGS. 1 and 3 , and an open position, such as shown in  FIGS. 2 and 4 , in response to a pressure wave in compartment  4 . More specifically, in the event of a build-up of gases, such as may occur during an arc fault event, pressure relief system  40  opens. Upon opening, the pressure wave carries the gases from compartment  4  to ventilation passage  20 . 
     As shown in  FIGS. 5 and 6 , pressure relief system  40  includes a closure or plate member  44  and a support bracket  46 . Plate member  44  includes a first surface  54  and an opposing, second surface  56 . An opening  58  extends through first and second surfaces  54  and  56 . Support bracket  46  extends from a first end  61  to a second end  62 . An intermediate portion  64  extends between first and second ends  61  and  62 . An opening  66  extends through intermediate portion  64  of support bracket  46 . Opening  66  may take the form of a threaded opening. A first flange  69  is arranged at first end  61  and a second flange  70  is arranged at second end  62 . First and second flanges  69  and  70  provide an attachment interface with second side wall  10  as well as a desired spacing from second surface  28 . 
     Pressure relief system  40  also includes a rod  80  that operatively connects plate member  44  to support bracket  46 . Rod  80  includes a first end portion  82  and a second end portion  83 . In the exemplary embodiment shown, rod  80  may take the form of a mechanical fastener or bolt (not separately labeled) having a head  85  at first end portion  82  and threads  87  at second end portion  83 . A washer  89  may be provided on rod  80  adjacent to head  85 . Rod  80  extends through opening  58  in plate member  44  and operatively connects with support bracket  46  at opening  66 . In this manner, first end portion  82  is cantilevered from support bracket  46 . Plate member  44  may transition from head  85  toward second end portion  83  between an open configuration ( FIG. 3 ) and a closed configuration ( FIG. 4 ). 
     A biasing member  94  provides a biasing force that urges plate member  44  toward head  85 . Thus, biasing member  94  urges plate member  44  into a normally closed configuration. In the exemplary embodiment shown, biasing member  94  takes the form of a coil spring  96  that extends about rod  80  between intermediate portion  64  of support bracket  46  and second surface  56  of plate member  44 . A spring seat  100  may be provided at second surface  56  to enhance alignment of coil spring  96  and rod  80 . Another spring seat (not shown) may be provided at intermediate portion  64  of support bracket  46 . 
     In accordance with an aspect of an exemplary embodiment, biasing member  94  includes a spring constant designed to allow plate member  44  to shift along rod  80  at a predetermined pressure. More specifically, a pressure wave  120 , such as shown in  FIG. 7 , may be generated in compartment  4 . Pressure wave  120  may result from gases generated during an arcing event. Pressure wave  120  includes an expected peak value of P p  at a time t p . Biasing member  94  includes a spring constant that is selected to allow plate member  44  to begin exposing opening  30  at a time t 1  before pressure wave  120  reaches a selected peak value P p . That is, biasing member  94  begins to deform or compress before pressure wave  120  reaches the expected peak value P p . The spring constant of biasing member  94  is also selected to allow plate member  44  to begin to return to the closed configuration at time t 2  that occurs after the selected peak value P p . In this manner, compartment  4  is never exposed to peak pressure during an arc fault event. Pressure relief system  40  begins to open before peak pressure is reached allowing pressure wave  120  to carry gases from compartment  4  before the peak is ever achieved thereby reducing the degree of pressure exposure to, for example, compartment  4 . Thus, pressure relief system  40  responds to pressure wave  120  before damage occurs in circuit breaker compartment  4 . 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.