Patent Publication Number: US-7911298-B2

Title: Electrical switching apparatus and trip actuator assembly therefor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus, such as circuit breakers. The invention also relates to trip actuator assemblies for circuit breakers. 
     2. Background Information 
     Electrical switching apparatus include, for example, circuit switching devices; circuit interrupters, such as circuit breakers; network protectors; contactors; motor starters; motor controllers; and other load controllers. Electrical switching apparatus such as circuit interrupters and, in particular, circuit breakers of the molded case variety, are well known in the art. See, for example, U.S. Pat. No. 5,341,191. 
     Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. Molded case circuit breakers typically include a pair of separable contacts per phase. The separable contacts may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to an overcurrent condition. Typically, such circuit breakers include an operating mechanism, which is designed to rapidly open and close the separable contacts, a trip unit, which senses overcurrent conditions in an automatic mode of operation, and a trip actuator assembly, which in response to such overcurrent conditions, is actuated by the trip unit to move the operating mechanism to a trip state, thereby moving the separable contacts to their open position. See, for example, U.S. Pat. Nos. 5,910,760; and 6,144,271. 
     It is sometimes desirable to integrate a new trip unit feature or a new or different type of trip unit into a circuit breaker. For example, it is sometimes desirable to integrate an electronic trip mechanism (e.g., without limitation, a flux shunt trip actuator) into the trip actuator assembly. Whether this is done during the assembly of a new circuit breaker or as a retrofit of an existing circuit breaker, it typically requires that numerous components be fit within the circuit breaker housing, where space is limited. Effectively arranging the trip actuator assembly within the circuit breaker housing such that it works well, yet does not require relatively significant modifications or alterations to the housing or to the circuit breaker in general, is a challenging endeavor. 
     There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in trip actuator assemblies therefor. 
     SUMMARY OF THE INVENTION 
     These needs and others are met by embodiments of the invention, which are directed to a trip actuator assembly for electrical switching apparatus such as, for example, circuit breakers, wherein the trip actuator assembly includes a frame and an interface assembly that enable the trip actuator assembly to operate effectively and to be secured in a desired orientation within a compartment of the circuit breaker housing. 
     As one aspect of the invention, a trip actuator assembly is provided for an electrical switching apparatus. The 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 housing includes an exterior, an interior, and a number of compartments disposed within the interior. The trip actuator assembly comprises: a trip actuator comprising an actuating element, the actuating element being structured to move among an unactuated position corresponding to the separable contacts of the electrical switching apparatus being closeable, and an actuated position corresponding to the separable contacts being tripped opened in response to a trip condition; a frame comprising a first end, a second end disposed opposite and distal from the first end, and a mounting portion disposed between the first end and the second end, the trip actuator being disposed at or about the mounting portion of the frame; and an interface assembly movably coupled to the frame, the interface assembly comprising an interface element, the interface element being structured to be disposed between the actuating element of the trip actuator and a portion of the operating mechanism of the electrical switching apparatus. When the actuating element of the trip actuator moves from the unactuated position toward the actuated position in response to the trip condition, the actuating element engages and moves the interface element, thereby moving the operating mechanism to trip open the separable contacts. The frame is structured to secure the trip actuator assembly in a desired orientation within a corresponding one of the number of compartments of the housing. 
     The interface assembly may further comprise a reset member movably coupled to the frame. The reset member may include a first end structured to be accessible from the exterior of the housing of the electrical switching apparatus, and a second end disposed opposite and distal from the first end of the reset member. The second end of the reset member may be cooperable with the interface element to reset the actuating element of the trip actuator from the actuated position to the unactuated position. The reset member may be a reset button. The reset button may be movable among a first position corresponding to the second end of the reset button not engaging the interface element, and a second position corresponding to the second end of the reset button engaging and moving the interface element, thereby moving the actuating element of the trip actuator toward the unactuated position. The interface assembly may further comprise a biasing element. The biasing element may bias the reset button toward the first position. 
     The frame may further comprise a first trip actuator restraint and a second trip actuator restraint. The trip actuator may be restrained between the first trip actuator restraint and the second trip actuator restraint, and the mounting portion of the frame may overlay at least a portion of the trip actuator. The first trip actuator restraint may be a first projection extending perpendicularly outwardly from the first end of the frame, and the second trip actuator restraint may be a second projection extending perpendicularly outwardly from the second end of the frame generally opposite the first projection. The first projection may include a tapered end, wherein the tapered end of the first projection is structured to cooperate with a portion of the corresponding one of the number of compartments of the housing of the electrical switching apparatus. 
     As another aspect of the invention, an electrical switching apparatus comprises: a housing including an exterior, an interior, and a number of compartments disposed within the interior; separable contacts enclosed by the housing; an operating mechanism for opening and closing the separable contacts; and a trip actuator assembly comprising: a trip actuator comprising an actuating element, the actuating element being movable among an unactuated position corresponding to the separable contacts being closeable, and an actuated position corresponding to the separable contacts being tripped opened in response to a trip condition, a frame comprising a first end, a second end disposed opposite and distal from the first end, and a mounting portion disposed between the first end and the second end, the trip actuator being disposed at or about the mounting portion of the frame, and an interface assembly movably coupled to the frame, the interface assembly comprising an interface element, the interface element being disposed between the actuating element of the trip actuator and a portion of the operating mechanism. When the actuating element of the trip actuator moves from the unactuated position toward the actuated position in response to the trip condition, the actuating element engages and moves the interface element, thereby moving the operating mechanism to trip open the separable contacts. The frame secures the trip actuator assembly in a desired orientation within a corresponding one of the number of compartments of the housing. 
     The operating mechanism may further comprise a trip bar and a generally planar element extending outwardly from the trip bar, and the interface element may include an elongated protuberance. When the actuating element of the trip actuator moves toward the actuated position in response to the trip condition, the elongated protuberance of the interface element may engage and move the generally planar element, thereby pivoting the trip bar and tripping open the separable contacts. 
     The electrical switching apparatus may be a circuit breaker, and the operating mechanism of the circuit breaker may further comprise a trip unit module. The trip unit module may comprise a sensor structured to sense current flowing through the separable contacts, and a processor structured to output a trip signal to the trip actuator of the trip actuator assembly responsive to the sensed current. When the sensed current is indicative of the trip condition, the trip signal may actuate the actuating element of the trip actuator thereby moving the actuating element to the actuated position to trip open the separable contacts. 
    
    
     
       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 exploded isometric view of a trip actuator assembly in accordance with an embodiment of the invention; 
         FIG. 2  is an assembled isometric view of the trip actuator assembly of  FIG. 1 , also showing a trip bar of a circuit breaker in accordance with an embodiment of the invention; 
         FIG. 3  is a top plan view of a circuit breaker employing the trip actuator assembly of  FIG. 2 ; and 
         FIG. 4  is a sectional view taken along line  4 - 4  of  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of illustration, embodiments of the invention are shown and described in association with a trip actuator for a trip unit of a three-pole circuit breaker, although it will become apparent that they are also applicable to a wide range of electrical switching apparatus having any number of poles. 
     Directional phrases used herein, such as, for example, left, right, top, bottom, up, down, clockwise and counterclockwise 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 terms “actuator” and “actuating element” refer to any known or suitable output mechanism (e.g., without limitation, trip actuator; solenoid) for an electrical switching apparatus and/or the element (e.g., without limitation, stem; plunger; lever; paddle; arm) of such mechanism which moves in order to manipulate another component of the electrical switching apparatus. 
     As employed herein, the term “fastener” shall mean a separate element or 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 term “trip condition” refers to any electrical event that results in the initiation of a circuit breaker operation in which the separable contacts of the circuit breaker are tripped open, and expressly includes, but is not limited to, electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions, receipt of an input trip signal, and a trip coil being energized. 
     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 a trip actuator assembly  100  for an electrical switching apparatus such as, for example, a circuit breaker  2  which is shown in  FIGS. 3 and 4 . The circuit breaker  2  includes a housing  4  having an exterior  6 , an interior  8 , and a number of compartments (see, for example, compartments  10  and  12  of  FIG. 3 ; one compartment  10  is shown in the sectional view of  FIG. 4 ) disposed within the interior  8 . Separable contacts  14  (shown in simplified form in  FIG. 3 ) are enclosed by the housing  4 , and an operating mechanism  16  (shown in simplified form in  FIG. 3 ) is structured to open and close the separable contacts  14  ( FIG. 3 ). 
     In the example of  FIGS. 3 and 4 , the operating mechanism  16  of the circuit breaker  2  includes a trip unit module  200 , which is coupled to a corresponding end of the circuit breaker housing  4 , as shown. The trip unit module  200  includes a number of sensors  202  (one is shown in  FIG. 4 ) structured to sense current flowing through the separable contacts  14  ( FIG. 3 ), and a processor (μP)  204  structured to output a trip signal (indicated generally by reference numeral  206  in  FIG. 3 ) to a trip actuator  102  (e.g., without limitation, a solenoid) of the trip actuator assembly  100  responsive to the sensed current. It will be appreciated that the trip module unit  200  and/or the components (e.g., without limitation, sensor(s)  202 ; processor (μP)  204 ; printed circuit board  208  ( FIG. 4 )) thereof could have a wide variety of alternative configurations (not shown), without departing from the scope of the invention. It will also be appreciated that a suitable interface such as, for example and without limitation, a FET transistor (not shown) may be employed to suitably buffer the trip signal  206  provided by the processor (μP)  204  to the trip actuator  102 . As will be discussed in greater detail hereinbelow, when the sensed current is indicative of a trip condition, as defined above, the trip signal  206  ( FIG. 3 ) energizes the trip actuator  102 , which actuates an actuating element  104  (e.g., without limitation, a plunger) 
     ( FIG. 4 ), thereby moving the actuating element  104  to trip open the separable contacts  14  ( FIG. 3 ) of the circuit breaker  2 . 
     As best shown in  FIGS. 1 and 2 , the example trip actuator  102  is a solenoid having a plunger  104  as the actuating element. The actuating element  104  is movable among an unactuated position ( FIG. 2 ) corresponding to the separable contacts  14  ( FIG. 3 ) of the circuit breaker  2  ( FIGS. 3 and 4 ) being closeable, and an actuated position (partially shown in phantom line drawing in  FIG. 4 ) corresponding to the separable contacts  14  ( FIG. 3 ) being tripped open in response to the trip condition. 
     The trip actuator assembly  100  further includes a frame  106  having first and second opposing ends  108 , 110  and a mounting portion  112  disposed therebetween. The trip actuator  102  is disposed at or about the mounting portion  112  of the frame  106 , as best shown in  FIG. 2 . The frame  106  also includes first and second trip actuator restraints  124 , 126 , which in the example shown and described herein are a first projection  124  extending perpendicularly outwardly from the first end  108  of the frame  106  and a second projection  126  extending perpendicularly outwardly from the second end  110  of the frame  106 , respectively. The second projection  126  is generally opposite the first projection  124  such that the trip actuator  102  is restrained between the first and second projections  124 , 126 . The first projection  124  includes a tapered end  128 , which is structured to cooperate (e.g., without limitation, conformingly fit together; nest) with a portion  22  of a corresponding one of the compartments  10  of the circuit breaker housing  4 , as shown in  FIG. 4 . In this manner, the frame  106  secures the trip actuator assembly  100  in the desired orientation within the compartment  10  (e.g., bottom compartment  10  from the perspective of  FIG. 3 ), with the mounting portion  112  of the frame  106  overlaying at least a portion of the trip actuator  102 , as shown. That is, a first side  142  of the mounting portion  112  faces the trip actuator  102 , and an opposing second side  144  faces the opposite direction toward the exterior  6  ( FIGS. 3 and 4 ) of the circuit breaker housing  4  ( FIGS. 3 and 4 ). A cavity  146 , which also faces the exterior  6  of the circuit breaker housing  4 , is formed in the second side  144 , as shown in  FIGS. 1-4 . It will be appreciated that the top cover of the circuit breaker housing  4  has been removed in  FIG. 3  to show internal structures of the circuit breaker  2 . 
     An interface assembly  114  is movably coupled to the frame  106 , and includes an interface element  116 , which is disposed between the actuating element  104  of the trip actuator  102  and a portion (see, for example, trip bar plate  20  of  FIG. 2 , discussed hereinbelow) of the circuit breaker operating mechanism  16  (indicated generally by reference numeral  16  in  FIG. 2 ; shown in simplified form in  FIG. 3 ). When the actuating element  104  of the trip actuator  102  moves from the unactuated position ( FIG. 2 ) toward the actuated position (partially shown in phantom line drawing in  FIG. 4 ) in response to the trip condition, the actuating element  104  engages and moves the interface element  116 , thereby moving (e.g., pivoting clockwise in the direction of arrow  30  from the perspective of  FIG. 4 ) a trip bar  18  of the operating mechanism  16  to trip open the separable contacts  14  ( FIG. 3 ). More specifically, the operating mechanism  16  of the example circuit breaker  2  includes a trip bar  18  and a generally planar element  20  (e.g., without limitation, a trip bar plate) extending outwardly from the trip bar  18 , as best shown in  FIG. 2 . The interface element  116  of the interface assembly  114  includes an elongated protuberance  140  extending perpendicularly outwardly therefrom. Thus, when the actuating element  104  of the trip actuator  102  moves toward the actuated position in response to the trip condition, the elongated protuberance  140  engages and moves (e.g., to the right from the perspective of  FIG. 4 ) the generally planar element  20 , thereby pivoting (e.g., clockwise in the direction of arrow  30  from the perspective of  FIG. 4 ) the trip bar  18 . See, for example, the elongated protuberance  140  and trip bar plate  20  pivoted thereby, shown in phantom line drawing in  FIG. 4 . This, in turn, trips open the separable contacts  14  ( FIG. 3 ) of the circuit breaker  2  ( FIGS. 3 and 4 ). 
     The interface assembly  114  of the example trip actuator assembly  100  further includes a reset button  118 , which is movably coupled to the frame  106  of the trip actuator assembly  100  at or about the second end  110  thereof. The reset member, which in the example shown and described herein is a reset button  118 , includes a first end  120 , which is accessible from the exterior  6  of the circuit breaker housing  4 , as shown in  FIGS. 3 and 4 , and a second end  122 , which is disposed opposite and distal from the first end  120 . The second end  122  of the reset button  118  is cooperable with the aforementioned interface element  116  to reset the actuating element  104  of the trip actuator  102  from the actuated position (partially shown in phantom line drawing in  FIG. 4 ) to the unactuated position (shown in solid line drawing in  FIG. 4 ; see also  FIG. 2 ). That is, the reset button  118  is movable among a first position ( FIG. 4 ) corresponding to the second end  122  of the reset button  118  not engaging the interface element  116 , and a second position ( FIG. 2 ) corresponding to the second end  122  of the reset button  118  engaging and moving (e.g., to the left from the perspective of  FIG. 2 ) the interface element  116 , thereby moving the actuating element  104  of the trip actuator  102  in a like manner, towards (e.g., to the left from the perspective of  FIG. 2 ) to its unactuated position ( FIG. 2 ). 
     To facilitate the above operation upon actuation of the reset button  118 , the interface element  116  includes an arcuate interface surface  134 , and the second end  122  of the reset button  118  includes a corresponding arcuate actuating surface  136 . When the reset button  118  is moved (e.g., downward from the perspective of  FIG. 2 ) from the first position toward the second position of  FIG. 2 , the arcuate actuating surface  136  of the second end  122  of the reset button  118  engages the arcuate interface surface  134  of the interface element  116 , and the two arcuate surfaces  134 , 136  cooperate to move (e.g., to the left from the perspective of  FIG. 2 ) the interface element  116 , thereby moving the actuating element  104  ( FIGS. 1 and 4 ) of the trip actuator  102  toward its unactuated position. 
     As best shown in  FIGS. 1 and 2 , the interface assembly  114  further includes a biasing element  130  (e.g., without limitation, a spring), which biases the reset button  118  toward the first position of  FIG. 4 . In the example shown and described herein, the spring  130  is disposed between the first end  120  of the reset button  118 , and a protrusion  132  ( FIG. 1 ), which extends outwardly from the frame  106  proximate the second end  110  thereof. It will, however, be appreciated that any other known or suitable biasing element (not shown) could be employed in any suitable alternative manner (not shown) to bias the reset button  118 . 
     Accordingly, the disclosed trip actuator assembly  100  provides a relatively compact sub-assembly, which fits in a desired orientation within a corresponding compartment  10  ( FIGS. 3 and 4 ) of the circuit breaker housing  4  ( FIGS. 3 and 4 ), yet provides an effective circuit breaker tripping device, for example and without limitation, for use with the trip unit module  200  ( FIGS. 3 and 4 ). 
     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.