Abstract:
A support for anchoring a trip unit of a circuit breaker to a base thereof to prevent separation of the trip unit from the base during a short circuit fault. The support has top-facing two locking tabs that snap into place behind a wall in a lug-receiving area of the base. The support also has an opening through which a terminal of the trip unit is received snugly. The locking tabs keep the support in place and prevent forces produced by gasses during a fault from forcing the trip unit away from the base. The terminal, attached to the trip unit, is retained by the opening, which transfers upward forces to the top of the support, which is positioned against a top section of the base. The snug fit by the terminal through the opening and retention of the support in the lug-receiving area during a fault increases post-fault dielectric performance.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure relates generally to circuit breakers, and, more particularly, to a support for anchoring a trip unit to a base of a circuit breaker, such as, for example during an electrical fault. 
       BACKGROUND 
       [0002]    A circuit breaker can include a removable trip unit that trips the circuit breaker in response to an electrical fault, such as a short circuit, thereby disconnecting the circuit breaker from a load that is being protected by the circuit breaker. The removable trip unit is installed into a base of the circuit breaker and screwed or bolted to the base. However, during a short circuit, explosive gasses produce a sudden and immense amount of internal pressure within the circuit breaker, lifting the trip unit from its installed location within the circuit breaker base. The stresses caused by the separation of the trip unit from the base can damage or dislodge the components of the circuit breaker, which can result in mis-operation or failure of the circuit breaker. A need exists for a more reliable support structure that keeps the trip unit on the base of the circuit breaker, such as, for example, during short circuit events. 
         [0003]    In addition, during a short circuit fault, debris under high pressure, typically in the form of gas and carbon, is expelled from the inside of the circuit breaker. Exhaust systems are provided for directing much of this debris safely away from the circuit breaker, but inevitably, some debris manages to escape through other areas besides through the exhaust vents. The electrically conductive carbon deposits that accumulate on the breaker near the lugs or wire connectors can form electrical couplings from one pole to another pole, creating a path for electrical current between adjacent lugs or wire connectors. When this occurs, the circuit breaker may fail safety tests. Enhancing the dielectric performance of the circuit breaker following a short circuit fault is desirable. A need exists for more robust dielectric protection following a short circuit fault. 
       BRIEF SUMMARY 
       [0004]    A U-shaped support piece has two tabs protruding from a top of the support and an opening in the back of the support sized to receive an electrical terminal of a trip unit. The support fits snugly into a lug-receiving area of a circuit breaker, where lugs attach cables carrying electrical current to the circuit breaker. The opening of the support is slid over the protruding terminal of the circuit breaker trip unit, and the upper part of the support is pushed against the base until the tabs snap into place behind a wall of the circuit breaker base into which the trip unit is installed. During a short circuit event, the forces created by the gasses try to push the trip unit away from the base, but the terminal of the trip unit is prevented from moving as it tries to push up against the opening of the support. The top of the support in turn pushes against the wall of the base, which keeps the trip unit from separating away from the base. 
         [0005]    The support stays in place during a short circuit fault, enhancing the dielectric performance of the circuit breaker when the support is made of a dielectric material, such as plastic. The support provides additional creepage distance between the circuit breaker connectors and other conductive parts of the breaker. 
         [0006]    The foregoing and additional aspects and implementations of the present disclosure will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments and/or aspects, which is made with reference to the drawings, a brief description of which is provided next. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The foregoing and other advantages of the present disclosure will become apparent upon reading the following detailed description and upon reference to the drawings. 
           [0008]      FIG. 1A  is a front view of a support according to the present disclosure; 
           [0009]      FIG. 1B  is a back view of the support shown in  FIG. 1A ; 
           [0010]      FIG. 2A  is a partial, cut-away, cross-sectional, perspective side view of the support shown in  FIG. 1A  partially installed into a lug-receiving area of a base of a circuit breaker; 
           [0011]      FIG. 2B  is a partial, cut-away, cross-sectional, perspective side view of the support shown in  FIG. 1A  installed into the lug-receiving area of the base; 
           [0012]      FIG. 3  is a partial, cut-away, top perspective view of a rear of the support shown in  FIG. 1A  as installed into the lug-receiving area of the base; 
           [0013]      FIG. 4  is a perspective, cut-away view of a 3-pole circuit breaker having three supports like the one shown in  FIG. 1A  exploded away from the lug-receiving areas of the circuit breaker in ready-to-be-installed positions, and a trip unit partially suspended above the base of the circuit breaker; 
           [0014]      FIG. 5  is a perspective, cut-away view of the circuit breaker shown in  FIG. 4  with the trip unit partially suspended above the base of the circuit breaker and the ampoule assemblies to which the terminals of the trip unit are connected; and 
           [0015]      FIG. 6  is an exploded view of the circuit breaker shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIGS. 1A and 1B  illustrate front and back views of a removable support  100  that keeps a removable trip unit of a circuit breaker  200  ( FIGS. 2A ,  4 ) from separating away from a base  204  ( FIG. 2A ) of the circuit breaker  200  and enhances the dielectric performance of the circuit breaker  200  following an electrical fault, such as a short circuit fault. The support  100  includes a back section  102  and oppositely facing wall sections  104 ,  106  that are positioned against corresponding side walls of a lug-receiving area  208   a  ( FIG. 2A ) of the circuit breaker  200 . The back section  102  and the wall sections  104 ,  106  form a generally U-shape. Each of the wall sections  104 ,  106  is orthogonal to the back section  102  of the support  100 . The back section  102  is positioned against a corresponding front section  206  ( FIG. 2A ) of the base  204  of the circuit breaker  200 . The support  100  includes a top section  108  having a top surface  120 . The top section  108  and the wall sections  104 ,  106  form a generally U-shaped piece. The top section  108  includes a first tab  110   a  spaced apart from a second tab  110   b,  both of which protrude away from the top surface  120  of the top section  108  of the support  100 . The tabs  110   a,b  include a back-sloped surface  118   a,b  ( FIGS. 1B ,  2 B) that slopes away from the back section  102  toward the front section  206  when the support  100  is installed into the lug-receiving area  208   a.  The back-sloped surfaces  118   a,b  allow the tabs  110   a,b  to snap into place behind the wall portion  212  of the base  204  when the support  100  is pushed into the lug-receiving area  208  toward the front section  206  of the base  204 . The tabs  110   a,b  are positioned on opposite sides of the top surface  120  of the top section  108  of the support  100  to secure the support  100  against the wall portion  212  at both of the opposite sides of the top surface  120 . 
         [0017]    With reference to  FIGS. 4 and 5 , the support  100  is made of a dielectric material, such as plastic or other electrically insulating material, for providing an electrically insulating barrier between a lug (not shown) inserted into the lug-receiving area  208   a  of the base  204 , or a wire connector (not shown) connected to the terminal  210   a  and the front section  206  of the base  204  against which the back portion  102  of the support  100  is positioned. The dielectric material of the support  100  provides over-surface and through-air clearance between the wire connectors that connect to the lugs installed into the lug-receiving area  208 , which enhances dielectric performance between adjacent terminals  210   a,b,c  ( FIG. 5 ) following a short circuit event. During a short circuit fault, debris produced by the fault typically in the form of carbon, is exhausted away from the circuit breaker by exhaust vents  402  ( FIG. 4 ). But some debris can escape through other parts of the circuit breaker  200 , including around the trip unit  202  (shown floating above its installed placement). The support  100  provides a dielectric barrier for any such exiting debris. Because the trip unit  202  remains securely anchored to the base  204  during a short circuit fault, no additional openings for the debris are created by the movement of the trip unit  202  away from the base  204 . 
         [0018]    The lug-receiving area  208   a  has a generally rectangular shaped access opening, and includes a side wall  216  ( FIG. 2A ), an oppositely facing side wall  218  ( FIG. 3 ), and a top section  214  ( FIG. 2A ). The top section  214  terminates at a wall portion  212 , against which the tabs  110   a,b  are received. 
         [0019]    The support includes a rectangular-shaped opening  112  formed in the back section  102  of the support  100 . The opening  112  has dimensions corresponding to a cross-sectional thickness of the electrical terminal  210   a  that extends through the opening  112 . By “corresponding to,” it is meant that the dimensions are slightly larger than the thickness so that the electrical terminal  210   a  is received snugly with minimal gaps around the opening  112  when the electrical terminal  210   a  is passed therethrough. An upper surface  114  of the back section  102  coincident with the opening  112  in the support  100  contacts a top surface  220  ( FIG. 2B ) of the electrical terminal  210   a  ( FIG. 2A ) of the trip unit  202 , which extends through the opening  112  of the support  100 . Correspondingly, a lower surface  115  of the back section  102  coincident with the opening  112  in the support  100  contacts a bottom surface  221  ( FIG. 2B ) of the electrical terminal  210   a.  Thus, little to no gap exists between the terminal  210   a  and the back section  100  in the opening  112 , presenting a barrier to any debris that is produced during an electrical fault. 
         [0020]    The electrical terminal  210   a  is connected to an ampoule assembly  502   a  ( FIGS. 5 and 6 ) of the circuit breaker  200 , which includes a movable contact. The back section  102  includes a calibration access screw hole  116  for permitting access to a calibration screw (not shown) in the trip unit for conventionally adjusting a parameter of the trip unit. 
         [0021]    The tabs  110   a,b  are received securely against the wall portion  212  of a top section  214  of the base  204  for preventing the removable trip unit  202  from moving away from the base  204  during an electrical fault. During a fault, pressure produced by the sudden gasses force the trip unit  202  upwards away from the base  204 . Because the terminal  210   a  is provided with the trip unit  202 , the terminal  210   a  wants to move with the trip unit  202 . However, the terminal  210   a  first encounters the surface  114  coincident with the opening  112 , and pushes up against that surface  114 . Those forces are transferred along the back section  102  of the support  100  to the top section  108 , which pushes up against the top section  214  of the lug-receiving area  208   a  of the base  204 . As a result, the trip unit  202  is securely held in place on the base  204  because the terminal  210   a  of the trip unit  202  is not free to move away from the base  204 . The support  100  prevents the trip unit  202  from moving away from the base  204  of the circuit breaker  200 . Because the trip unit  202  remains securely in place during an electrical fault, the dielectric performance of the circuit breaker  200  is enhanced because the opportunity for exhausted debris to coat the breaker surfaces is minimized by forcing the debris to find another pathway out of the circuit breaker  200 . 
         [0022]    The support  100  is positioned in the lug-receiving area  208   a  of the base  204  for receiving a conventional lug (not shown) therein.  FIG. 2A  illustrates the support  100  partially installed into the lug-receiving area  208   a  of the base  204  and slightly twisted toward the viewer for ease of illustration to show the tabs  110   a,b  of the support  100 . In practice, the support  100  should be installed by positioning the back section  102  so that it is parallel with the front section  206  of the base  204 . The opening  112  of the support  100  is aligned with the terminal  210   a  that is received in the opening  112  as the support  100  is pushed toward the front section  206  of the base  204 . 
         [0023]    In  FIG. 2B , the support  100  is shown installed into the lug-receiving area  208   a  of the base  204 . The tab  110   b  is shown positioned behind the wall portion  212  of the base  204 , and the surface  114  of the support  100  contacts the upper surface of the terminal  210   a.  Any force that tries to move the terminal  210   a  (and correspondingly the trip unit  202  to which the terminal  210   a  is attached) away from the base  204  will be opposed by the surface  114  of the support  100 , the top section  108  of the support  100 , and the top section  214  of the base  204 . In this installed position, the back section  102  of the support  100  is positioned against the front section  206  of the lug-receiving area  208   a  of the base  204 . The top surface  120  of the support  100  is positioned against the top section  214  of the lug-receiving area  208   a  of the base  204 , the tabs  110   a,b  are positioned against the wall portion  212  of the base  204 , and the surface  114  of the back section  102  coincident with the opening  112  of the support  100  is positioned against and contacts the top surface  220  of the terminal  210   a.    
         [0024]      FIG. 3  illustrates a cut-away perspective view of a rear portion of the circuit breaker  200  to reveal the tabs  110   a,b  positioned against the wall portion  212  of the base  204 . The terminal  210   a,  which can be connected to an electrical load (not shown) terminates in the interior of the circuit breaker  200  and receives a trip-unit-to-ampoule screw  302   a,  which attaches the trip unit  202  to an ampoule assembly  502   a  ( FIG. 5 ). The front section  206  ( FIG. 2B ) of the base has been removed to show the back section  102  of the support  100  installed within the lug-receiving area  208   a.  The back-sloped surfaces  118   a,b  of the tabs  110   a,b  can be seen as well in this view, and these sloped surfaces allow the tabs  110   a,b  to be snapped into place behind the wall portion  212  of the base  204 . To remove the support  100 , a screwdriver or similar tool can be inserted into a gap  304  between the top surface  120  of the support  100  and the top section  214  of the lug-receiving area  208   a,  and pressed downward slightly to release the tabs  110   a,b  from the wall portion  212  of the base  204 . Once the supports  100  are removed from the lug-receiving areas  208 , the trip unit can be removed from the base. 
         [0025]      FIG. 4  illustrates a partially cut-away three-pole circuit breaker  200  with three supports  100 , one for each pole. Each support  100  is like the support  100  illustrated and described in connection with  FIGS. 1A-1B . The ampoule assemblies and other internal components of the circuit breaker  200  and the trip unit  202  have been removed for ease of illustration. A portion of the base  204  is cut-away to reveal part of the trip unit  202 . There are three lug-receiving areas  208   a,b,c , each receiving a corresponding electrical terminal  210   a,b,c  of the trip unit  202 . Typically, these terminals  210   a,b,c  are connected to a load (not shown) protected by the circuit breaker  200 , and can be called load terminals. Wired connections (including cable conductors) are attached through lugs (not shown) installed into the lug-receiving areas  210   a,b,c  to the terminals  210   a,b,c  for carrying electrical current to the load being protected by the circuit breaker  200 . 
         [0026]    In  FIG. 5 , more details of the circuit breaker  200  are shown, including the trip unit  202  and three ampoule assemblies  502   a,b,c . Each ampoule assembly  502 , a,b,c  is connected to a respective terminal  210   a,b,c  of the trip unit. Each ampoule assembly  502   a,b,c  conventionally includes a movable contact and a stationary contact, which separate from one another upon detection of an electrical fault by the circuit breaker  200  to break the electrical connection between the load side of the circuit breaker and the line side of the circuit breaker, disconnecting the load from line current being supplied by the line side (or vice versa). The trip unit  202  is shown slightly elevated over the base  204  in an intermediate installed position. To install the trip unit  202 , it is positioned into the base  204 , and the screws  302  ( FIG. 6 ) are screwed into the ampoules  502 , which in turn are securely coupled to the base  204 . 
         [0027]      FIG. 6  is an exploded perspective view of some of the primary components of the circuit breaker  200 . An auxiliary cover  602  is placed over a handle  604 . A pressure cover  608  is placed adjacent to the ampoule assemblies  502   a,b,c , which have corresponding line terminals  610   a,b,c  for connection to a respective phase of a conductor carrying current from a power supply. To install the trip unit  202  into the circuit breaker  200 , the trip unit  202  is lowered into the base  204 , and the screws  302   a,b,c  are screwed into the respective ampoule assemblies  502   a,b,c , which are in turn securely coupled to the base  204 , optionally through a piston trip assembly (not shown). Then, three supports  100  are installed into the corresponding lug-receiving areas  208  of the base  204  until they snap in place. 
         [0028]    Although the support  100  has been described as being composed of a dielectric material, in other implementations in which it is not needed as a dielectric, the support  100  can be made of metal, such as steel. Instead of being inserted into the trip unit end of the circuit breaker, they can be installed into area where the line terminals  610  are attached to the ampoules  502 . Finally, the support  100  is not necessarily for use only during an electrical fault. It can be generally used to secure the major, separate components of the circuit breaker together, such as the trip unit, base, and ampoules, inhibiting these major components from separating away from one another. 
         [0029]    While particular implementations and applications of the present disclosure have been illustrated and described, it is to be understood that the present disclosure is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations can be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.