Patent Publication Number: US-9406473-B2

Title: Circuit breaker terminal shield

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2013-0134335, filed on Nov. 6, 2013, the contents of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a circuit breaker, and more particularly, to a circuit breaker including a lug-type terminal block. 
     2. Background of the Invention 
     In general, a circuit breaker is an electrical device that manually opens and closes an electrical circuit by a handle, or that protects load devices and circuits by detecting an abnormal current such as a short current or a fault current and automatically breaking the circuits. 
     The circuit breaker normally maintains a conductive status when a rated current flows, but performs a breaking operation when a fault current occurs. To this end, a fixed contact and a moving contact maintain a closed status when a normal current flows. 
     However, when a fault current has occurred, a trip unit detects the fault current and transmits a signal to a switching mechanism. Then, the switching mechanism is released. Once the switching mechanism is released, the fixed contact and the moving contact are separated from each other. Accordingly, the circuit breaker is able to safely break the accident current. 
     The circuit breaker includes an arc suppressor on one side of the switching mechanism. The arc suppressor blows out and suppresses an arc generated when the fixed contact and the moving contact are separated from each other. 
     The circuit breaker is divided into a surface-type terminal block, a reversible terminal block, a plug-in type terminal block, and a lug-type terminal block, depending on the connecting method of a terminal block for connecting the wire of a power supply side and the wire of a load side. 
     The lug-type terminal block is usually used in the U.S. market. 
       FIG. 1  is a perspective view showing a conventional circuit breaker using a lug-type terminal block.  FIG. 2  is a cross-sectional view taken along the line I-I of  FIG. 1 . 
     Hereinafter, the conventional circuit breaker using a lug-type terminal block will be described below with reference to the accompanying  FIGS. 1 and 2 . 
     That is, a main body  20  is placed within an outer casing  10  of the conventional circuit breaker. 
     A mechanism (not shown) including a fixed contact  40  and a moving contact  30 , an arc suppressor  24 , a trip unit (not shown), etc are mounted within the main body  20  for circuit breaking purposes. 
     A terminal portion  42  is formed on an end of the fixed contact  40  so as to be exposed to the exterior of the main body  20 . A lug-type terminal block  50  for connecting the terminal portion  42  and a wire (not shown) is attached to the terminal portion  42 . 
     The bottom side of the lug-type terminal block  50  is in contact with the terminal portion  42 , and one side thereof is positioned facing the main body  20 . 
     However, the lug-type terminal block  50  is positioned in proximity to the outer surface  22  of the arc suppressor  24  in the main body, so that the distance between them is fairly small. As such, an arc conduction path may be formed between the lug-type terminal block  50  and the arc suppressor  24  of the main body  20 . Accordingly, dielectric breakdown might occur to the terminal portion through the lug-type terminal block in the main body. 
     Taking this into consideration, the terminal portion  42  and the lug-type terminal block  50  may be spaced far from the main body  20 . In this case, dielectric breakdown can be suppressed. However, this requires increasing the size of the circuit breaker, thus leading to a rise in manufacturing costs and imposing limitations on installation space. 
     SUMMARY OF THE INVENTION 
     Therefore, an aspect of the present invention is to provide a circuit breaker which is capable of suppressing the occurrence of dielectric breakdown by forming an arc conduction path between a lug-type terminal block and a main body, without increasing the size of the circuit breaker. 
     To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a circuit breaker including: a main body housing circuit-breaking parts; a terminal portion exposed outside the main body; a lug-type terminal block attached to the terminal portion and connecting a wire to the terminal portion; and an insulating member provided between the lug-type terminal block and the main body. 
     The lug-type terminal block may be in as close proximity as possible to the main body as long as the lug-type terminal block does not come into contact with the main body, in order to reduce the size of the circuit breaker. 
     The insulating member may be supported on at least either the lug-type terminal block or the main body. 
     The insulating member may include an insulating surface that is formed to cover a side of the lug-type terminal block facing the main body. 
     According to one embodiment of the present invention, the insulating member may further include a supporting surface that extends from the insulating surface and is inserted between the terminal portion and the lug-type terminal block. 
     According to another embodiment of the present invention, the insulating member may further include a supporting surface that extends from the insulating surface and is inserted between the terminal portion and the main body. 
     According to yet another embodiment of the present invention, the side of the lug-type terminal block may include: a first side facing the main body in parallel; and a second side extending from the first side and facing the main body at a slant. 
     The first side may be in as close proximity to the main body as possible as long as the first side does not come into contact main body. 
     The distance from the second side to the main body may become smaller as the second side gets nearer to the first side and larger as the second side gets farther from the first side. 
     The insulating surface of the insulating member may include: a first insulating surface that covers the first side; and a second insulating surface that extends from the first insulating surface and covers the seconds surface. 
     The insulating member may further include a supporting surface that extends from the first insulating surface and is inserted between the terminal portion and the lug-type terminal block. 
     Alternatively, the insulating member may further include a supporting surface that extends from the first insulating surface and is inserted between the terminal portion and the main body. 
     The insulating member may be made of insulating paper. 
     The insulating paper may be Nomex paper. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a perspective view showing a conventional circuit breaker; 
         FIG. 2  is a cross-sectional view taken along the line I-I of  FIG. 1 ; 
         FIG. 3  is a perspective view showing a circuit breaker according to the present invention; 
         FIG. 4  is a perspective view showing an insulating member of  FIG. 3 ; and 
         FIG. 5  is a cross-sectional view taken along the line II-II of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, an exemplary embodiment of the present invention will be described with reference to the accompanying drawings. 
       FIG. 3  is a perspective view showing a circuit breaker according to the present invention.  FIG. 4  is a perspective view showing an insulating member of  FIG. 3 .  FIG. 5  is a cross-sectional view taken along the line II-II of  FIG. 3 . 
     As shown in  FIGS. 3 to 5 , the circuit breaker according to the present invention may include: a main body  20  housing circuit-breaking parts; a terminal portion  42  exposed outside the main body  20 ; a lug-type terminal block  50  attached to the terminal portion  42  and connecting a wire to the terminal portion  42 ; and an insulating member  160  provided between the lug-type terminal block  50  and the main body  20 . 
     The main body  20  may house the circuit-breaking parts and be placed within an outer casing  10 . 
     The circuit-breaking parts include a switching portion (not shown) having a fixed contact  40  and a moving contact  30 , an arc suppressor  24  for suppressing an arc generated from the switching portion (not shown), and a trip unit (not shown) for detecting an overload or momentary current and a short current. They are well known components and thus detailed descriptions will be omitted. 
     The terminal portion  42  may be formed on an end of the fixed contact  40  exposed to the exterior of the main body  20 . 
     The lug-type terminal block  50  for connecting the terminal portion  42  and a wire (not shown) may be attached to the terminal portion  42 . 
     The lug-type terminal block  50  may be in the shape of a rectangle with a sloped side at an edge portion. 
     With reference to the drawings, the edge portion may be a region where a back side perpendicular to the bottom side  52  and a top side  58  facing the bottom side  52  meet. 
     For convenience of explanation, the back side of the lug-type terminal block is referred to as a first side  54 , and the sloped side is referred to as a second side  56 . 
     The bottom side  52  of the lug-type terminal block  50  may be in contact with the terminal portion  42 , and the first side  54  and the second side  56  may be positioned facing the outer surface  22  of the arc suppressor in the main body. 
     The first side  54  may be in as close proximity to the outer surface  22  of the arc suppressor in the main body as possible as long as it does not come into contact with the outer surface  22  of the arc suppressor in the main body, and may be positioned parallel to the outer surface  22  of the arc suppressor in the main body. 
     The second side  56  may be slanted to the outer surface  22  of the arc suppressor in the main body. In other words, the distance from the second side  56  to the outer surface  22  of the arc suppressor in the main body may become larger as it goes from the first side  54  toward the top side  58 . 
     The reason why the lug-type terminal block  50  includes the second side  56 , the first side  54  is positioned adjacent to the outer surface  22  of the arc suppressor in the main body, and the second side  56  is inclined to the outer surface  22  of the arc suppressor in the main body is to make the circuit breaker as small in size as possible and facilitate the blowout of an arc. 
     More specifically, the outer surface  22  of the arc suppressor in the main body may include an arc outlet at the top facing the second side  56  to blow out an arc. 
     The lug-type terminal block  50  may be positioned in as close proximity to the main body  20  as possible as long as it does not come into contact with the main body  20 , in order to make the circuit breaker as small in size as possible. 
     However, if the lug-type terminal block  50  is positioned in proximity to the main body  20 , the top of the lug-type terminal block  50  where the top side  58  is positioned may block the arc outlet because the lug-type terminal block  50  has a predetermined height from the bottom side  52  to the top side  58 . Accordingly, an arc may not be properly blown out. 
     As such, the lug-type terminal block  50  may be positioned in as close proximity to the main body  20  as possible in order to make the circuit breaker as small in size as possible, and may include the second side  56  at the part facing the arc outlet to properly blow out an arc. 
     The insulating member  160  may be positioned between the lug-type terminal block  50  and the main body  20  to suppress dielectric breakdown caused by an arc conduction path formed between the lug-type terminal block  50  and the arc suppressor  24  of the main body  20 . 
     The insulating member  160  may include an insulating surface  162  that is formed to cover the side facing the outer surface  22  of the arc suppressor in the main body of the lug-type terminal block  50 . 
     Moreover, the insulating member  160  may include a supporting surface  164  that is bent and extends from the insulating surface  162  and is inserted between the terminal portion  42  and the main body  20 . 
     In this case, the insulating member  164  may be made of insulating paper, such as Nomex paper. 
     In this embodiment, the insulating member  160  may include the supporting surface  164 , and the supporting surface  164  may be inserted between the terminal portion  42  and the main body  20 . As such, the insulating member  160  may be supported on the main body  20 . 
     Alternatively, the supporting surface  164  may be inserted between the terminal portion  42  and the bottom side  52  of the lug-type terminal block  50 , and therefore the insulating may be supported on the lug-type terminal block  50 . 
     Alternatively, the insulating member  160  may include only the insulating surface  162  but not the supporting surface  164 , and the insulating surface  162  may be attached to the side facing the outer surface  22  of the arc suppressor in the main body of the lug-type terminal block  50  and supported on the lug-type terminal block  50 . 
     The insulating surface  162  may include a first insulating surface  162   a  that covers the first side  54  of the lug-type terminal block  50  and a second insulating surface  162   b  that is bent and extends from the first insulating surface  162   a  and covers the seconds surface  56  of the lug-type terminal block  50 . 
     In this case, the supporting surface  164  may be bent and extends from the first insulating surface  162   a  to the opposite side of the second insulating surface  162   b.    
     In these drawings, the same components as those in the prior art are given the same reference numerals. 
     Now, operational effects of the circuit breaker according to the present invention will be described. 
     That is, when a rated current flows, the circuit breaker normally maintains a conductive status, keeping the moving contact  30  and the fixed contact  40  in contact with each other. 
     However, when an abnormal current, such as a fault current, occurs, the circuit breaker performs a breaking operation as the moving contact  30  is separated from the fixed contact  40 . 
     The first side  54  and second side  56  of the lug-type terminal block  50  are positioned in proximity to the outer surface  22  of the arc suppressor in the main body, so that the distance between them may be fairly small. 
     Accordingly, dielectric breakdown might occur due to an arc conduction path formed between the lug-type terminal block  50  and the arc suppressor  24  in the main body  20 . 
     On the other hand, in the circuit breaker according to the present invention, the insulating member  160  made of an insulating material may be positioned between the lug-type terminal block  50  and the main body  20 , more precisely, between the first and second sides  54  and  56  of the lug-type terminal block  50  and the outer surface  22  of the arc suppressor in the main body. 
     As such, the circuit breaker according to the present invention can suppress the formation of an arc conduction path between the lug-type terminal block  50  and the main body  20 . 
     Therefore, the circuit breaker according to the present invention can suppress dielectric breakdown occurring to the terminal portion  42  through the lug-type terminal block  50  in the main body  20 , without increasing the size of the circuit breaker. 
     As a consequence, the circuit breaker according to the present invention can suppress incomplete arc suppression and improve the reliability of circuit breaking.