Patent Publication Number: US-9842708-B1

Title: Circuit breaker latch mechanism integrated into the rotor assembly

Description:
BACKGROUND 
     The field of the disclosure relates generally to circuit breakers and, more particularly, to circuit breakers including rotatable contact arms. 
     Circuit breakers are often used to protect, in a residential, industrial, utility, or commercial environment, against overcurrent conditions, ground fault conditions, or other system anomalies that are undesirable and require the circuit breaker to interrupt the flow of current through the circuit breaker. In some circuit breakers, a movable contact is separated from a stationary contact when the circuit breakers experience an overcurrent condition, such as a short circuit event. Separating the circuit breaker contacts, generally referred to as “tripping” the circuit breaker when caused by protection reasons or “opening” the circuit breaker when caused by control reasons, interrupts the flow of current through the circuit breaker. 
     In industrial settings, for example, the circuit breaker serves to prevent damage to equipment and machines that, in many cases, represent a significant investment by a business and on whose operation the business relies. The circuit breaker carries out this function by interrupting electrical current between the equipment and a power center or transformer when the circuit breaker contacts are separated. However, sometimes the circuit breaker contacts may not remain separated during an overcurrent condition. For example, sometimes after separating from the stationary contact, the movable contact rebounds and moves back towards the stationary contact. Accordingly, at least some known circuit breakers include retention systems that retain the movable contact in a position separated from the stationary contact. However, the retention systems increase the amount of force required to separate the contacts. As a result, the contacts do not fully separate to interrupt the flow of current through the circuit breaker in some overcurrent conditions, which may impact operation of equipment and machines. Moreover, the retention systems increase the cost and time required to assemble the circuit breakers. 
     BRIEF DESCRIPTION 
     In one aspect, a circuit breaker is provided. The circuit breaker includes an electrically insulative case and a rotor assembly disposed within the electrically insulative case. The rotor assembly includes a contact arm and a rotor that is rotatable relative to the electrically insulative case. The contact arm is coupled to the rotor and movable between a first position in which a conductive path is closed and a second position in which the conductive path is open. The rotor assembly also includes a latch mechanism coupled to the rotor. The latch mechanism retains the contact arm in the second position during a short circuit event. The latch mechanism is spaced from the contact arm when the contact arm is in the first position. The latch mechanism engages the contact arm when the contact arm is in the second position. 
     In another aspect, a rotor assembly for a circuit breaker is provided. The rotor assembly includes a contact arm and a rotor that is rotatable relative to an electrically insulative case. The contact arm is coupled to the rotor and movable between a first position in which a conductive path is closed and a second position in which the conductive path is open. The rotor assembly also includes a latch mechanism coupled to the rotor. The latch mechanism retains the contact arm in the second position during a short circuit event. The latch mechanism is spaced from the contact arm when the contact arm is in the first position. The latch mechanism engages the contact arm when the contact arm is in the second position. 
     In yet another aspect, a method of manufacturing a circuit breaker is provided. The method includes coupling a rotor to the electrically insulative case. The rotor is rotatable relative to the electrically insulative case. The method also includes coupling an operating mechanism to the rotor. Actuation of the operating mechanism causes the rotor to rotate. The method further includes coupling a movable contact to the rotor. The movable contact is movable between a first position in which a conductive path is closed and a second position in which the conductive path is open. The method also includes coupling a latch mechanism to the rotor. The latch mechanism inhibits movement of the movable contact when the movable contact is in the second position. The latch mechanism is spaced from the movable contact when the movable contact is in the first position. The latch mechanism engages the movable contact when the movable contact is in the second position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a section view of a circuit breaker assembly including a contact arm of a rotor assembly in a second position; 
         FIG. 2  is a perspective view of a portion of the circuit breaker assembly shown in  FIG. 1  with the contact arm in a first position; 
         FIG. 3  is a perspective view of a rotor assembly of the circuit breaker assembly shown in  FIG. 1 ; 
         FIG. 4  is a section view of a rotor assembly of the circuit breaker shown in  FIG. 3  with a contact arm and latch mechanism disengaged, wherein the contact arm is in a first position and the latch mechanism is in a neutral position; 
         FIG. 5  is a section view of the rotor assembly shown in  FIG. 4  with the contact arm and latch mechanism engaged, wherein the latch mechanism maintains the contact arm in a second position; 
         FIG. 6A  is a schematic view of a latch mechanism in a neutral position and a contact arm of the rotor assembly shown in  FIG. 4  in a first position; 
         FIG. 6B  is a schematic view of the latch mechanism in a displaced position and the contact arm moving from the first position toward a second position; 
         FIG. 6C  is a schematic view of the latch mechanism moving toward the neutral position and the contact arm moving toward the second position; 
         FIG. 6D  is a schematic view of the latch mechanism in a neutral position and retaining the contact arm in the second position; 
         FIG. 7A  is a schematic view of the latch mechanism in a neutral position and the contact arm in the second position; 
         FIG. 7B  is a schematic view of the latch mechanism in the displaced position and the contact arm moving from the second position toward the first position; 
         FIG. 7C  is a schematic view of the latch mechanism in the neutral position and the contact arm in the second position; 
         FIG. 8  is a perspective view of an alternative rotor assembly for the circuit breaker assembly shown in  FIG. 1 ; 
         FIG. 9  is a section view of a circuit breaker assembly including a plurality of contact arms; 
         FIG. 10  is a perspective view of a portion of the circuit breaker assembly shown in  FIG. 9 ; and 
         FIG. 11  is a graph showing torque profiles of rotor assemblies. 
     
    
    
     Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems including one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein. 
     DETAILED DESCRIPTION 
     In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. 
     The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. 
     “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. 
     Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “substantially,” and “approximately,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. 
     Exemplary embodiments of circuit breakers and methods of manufacturing circuit breakers are described herein. The circuit breakers generally include a contact arm that moves between a first position engaged with a stationary contact and a second position disengaged from the stationary contact. In some embodiments, the contact arm is retained in the second position by a latch mechanism. In particular, the latch mechanism is spaced from the contact arm when the contact arm is in the first position and the latch mechanism engages the contact arm when the contact arm moves to the second position during a short circuit event. 
       FIG. 1  is a section view of a circuit breaker  100 .  FIG. 2  is a perspective view of a portion of circuit breaker  100 . Circuit breaker  100  includes a case  102 , a load strap  104 , a line strap  106 , a rotor assembly  108 , and an operating mechanism  110 . Case  102  electrically insulates circuit breaker  100  such that electrical current is inhibited from passing through case  102  to the surrounding environment. Operating mechanism  110  is operatively coupled to rotor assembly  108  and rotates rotor assembly  108  upon actuation of operating mechanism  110 . In alternative embodiments, circuit breaker  100  includes any components that enable circuit breaker  100  to operate as described herein. For example, in some embodiments, circuit breaker  100  includes a plurality of cases  102 , load straps  104 , line straps  106 , rotor assemblies  108 , and/or operating mechanisms  110 . In the exemplary embodiment, circuit breaker  100  is coupled to a circuit such that circuit breaker  100  controls flow of electric current through the circuit. In particular, when operating mechanism  110  of circuit breaker  100  is actuated and rotor assembly  108  is rotated, the flow of electric current through the circuit coupled to circuit breaker  100  is stopped. 
     In the exemplary embodiment, rotor assembly  108  includes a rotor  112  and a contact arm  114 . Contact arm  114  includes a load contact  116  selectively contacting load strap  104  and a line contact  118  selectively contacting line strap  106 . Contact arm  114  is coupled to rotor  112  such that rotation of rotor  112  causes contact arm  114  to move between a first position (shown in  FIG. 2 ) where contact arm  114  engages load strap  104  and line strap  106  and a second position (shown in  FIG. 1 ) where contact arm  114  is disengaged from load strap  104  and line strap  106  due to a short circuit event. Accordingly, contact arm  114  is a movable contact and load strap  104  and line strap  106  are stationary contacts. In alternative embodiments, circuit breaker  100  includes any contacts that enable circuit breaker  100  to operate as described herein. 
     Also, in the exemplary embodiment, each of load strap  104  and line strap  106  includes a first leg  120 , a second leg  122 , and a curved segment  124  interconnecting first leg  120  and second leg  122 . As such, load strap  104  and line strap  106  have a U-shape. Load strap  104  and line strap  106  include an electrically conductive material to facilitate current flowing through load strap  104  and line strap  106 . During operation of circuit breaker  100 , at least one of load strap  104  and line strap  106  generates repulsive forces when a predetermined current flows through load strap  104  and/or line strap  106 . In particular, the reverse loops of load strap  104  and line strap  106  generate repulsive forces that repel load contact  116  and line contact  118  from load strap  104  and line strap  106 . As a result, contact arm  114  is disengaged from load strap  104  and line strap  106  and current is inhibited from flowing through the circuit coupled to circuit breaker  100 , i.e., circuit breaker  100  is tripped. In alternative embodiments, load strap  104  and line strap  106  have any configuration that enables circuit breaker  100  to operate as described herein. 
       FIG. 3  is a perspective view of rotor assembly  108 . Rotor  112  of rotor assembly  108  includes a first end  128 , a second end  130 , a sidewall  132 , and rotor pins  134 . In the illustrated embodiment, first end  128  and second end  130  are circular and rotor  112  has a cylindrical shape. Sidewall  132  extends between first end  128  and second end  130  and defines openings  136 . Rotor pins  134  extend between first end  128  and second end  130  adjacent openings  136 . Contact arm  114  extends at least partially through an interior of rotor  112  and through openings  136 . Moreover, contact arm  114  has some freedom of movement relative to rotor  112 . In alternative embodiments, rotor  112  has any configuration that enables circuit breaker  100  to operate as described herein. 
       FIG. 4  is a section view of rotor assembly  108  with contact arm  114  and latch mechanisms  126  disengaged.  FIG. 5  is a section view of rotor assembly  108  with contact arm  114  and latch mechanisms  126  engaged. Rotor assembly  108  includes latch mechanisms  126  to retain contact arm  114  in the second position when contact arm  114  moves to the second position without rotation of rotor  112 . Latch mechanisms  126  are coupled to opposite sides of rotor  112 . As shown in  FIG. 4 , each latch mechanism  126  is spaced from contact arm  114  when contact arm  114  is in the first position. As shown in  FIG. 5 , each latch mechanism  126  engages contact arm  114  when contact arm  114  is in the second position and rotor  112  has not rotated. Accordingly, latch mechanisms  126  retain contact arm  114  in the second position when circuit breaker  100  is subject to high current. Moreover, as will be discussed below, latch mechanisms  126  reduce the torque required to position contact arm  114  in the second position and increase the torque required to return contact arm  114  to the first position. As a result, latch mechanisms  126  allow circuit breaker  100  to hold contact arm  114  in the second position under lower level overcurrent conditions and facilitate circuit breaker  100  remaining in an open position until operating mechanism  110  is actuated to reset circuit breaker  100  and settle at a trip open position. 
     In the exemplary embodiment, each latch mechanism  126  includes a head  140  and a biasing mechanism  142 . Head  140  engages contact arm  114  and is movable between a neutral position and a displaced position. In the exemplary embodiment, contact arm  114  further includes a catch  144  to engage head  140 . Biasing mechanism  142  resists displacement of head  140  and biases head  140  towards the neutral position. In particular, biasing mechanism  142  extends between head  140  and rotor  112  to exert forces on rotor  112  and head  140 . In the illustrated embodiment, biasing mechanism  142  includes a plurality of leaf springs. In alternative embodiments, latch mechanism  126  has any configuration that enables rotor assembly  108  to function as described herein. 
     Also, in the exemplary embodiment, latch mechanism  126  is coupled to rotor pin  134  such that latch mechanism  126  rotates with rotor  112 . In particular, latch mechanism  126  is coupled to rotor pin  134  such that rotor pin  134  extends between head  140  and biasing mechanism  142 . As a result, latch mechanism  126  pivots about rotor pin  134 . Coupling latch mechanism  126  to rotor  112  reduces the number of additional parts required to incorporate latch mechanism  126  into circuit breaker  100 . Moreover, latch mechanism  126  enables rotor assembly  108  to have a compact size. In alternative embodiments, latch mechanism  126  is coupled to any portions of circuit breaker  100  that enable latch mechanism  126  to function as described herein. 
     Moreover, in the exemplary embodiment, latch mechanism  126  is made of a flexible material with structural strength. In addition, head  140  and biasing mechanism  142  are integrally formed as a single piece. In alternative embodiments, latch mechanism  126  is made of any material and in any manner that enables latch mechanism  126  to function as described herein. For example, in some embodiments, latch mechanism  126  is made of any of the following materials, without limitation: thermoplastics, metals, springs, and combinations thereof. 
       FIG. 6A  is a schematic view of latch mechanism  126  in a neutral position and contact arm  114  in a first position.  FIG. 6B  is a schematic view of latch mechanism  126  in a displaced position and contact arm  114  moving from the first position toward a second position.  FIG. 6C  is a schematic view of latch mechanism  126  moving toward the neutral position and contact arm  114  moving toward the second position.  FIG. 6D  is a schematic view of latch mechanism  126  in the neutral position and latch mechanism  126  retaining contact arm  114  in the second position.  FIG. 7A  is a schematic view of latch mechanism  126  in the neutral position and contact arm  114  in the second position.  FIG. 7B  is a schematic view of latch mechanism  126  in the displaced position and contact arm  114  moving from the second position toward the first position.  FIG. 7C  is a schematic view of latch mechanism  126  in the neutral position and contact arm  114  in the second position. 
     During a high fault current event, contact arm  114  moves to the second position and contacts latch mechanism  126  to cause head  140  to move from the neutral position to the displaced position. When head  140  is displaced, biasing mechanism  142  biases head  140  towards the neutral position and head  140  engages catch  144 . As a result, contact arm  114  is retained in the second position by the engagement of head  140  and catch  144 . Latch mechanism  126  and contact arm  114  are disengaged when operating mechanism  110  (shown in  FIG. 1 ) is actuated to cause rotation of rotor  112 . Rotation of rotor  112  causes latch mechanism  126  to move away from contact arm  114 . However, case  102  (shown in  FIG. 1 ) inhibits contact arm  114  moving with rotor  112  and latch mechanism  126 . As a result, head  140  is displaced by contact arm  114  and disengages from catch  144  as latch mechanism  126  moves away from contact arm  114 . In alternative embodiments, latch mechanism  126  and contact arm  114  engage in any manner that enables circuit breaker  100  to operate as described herein. 
     In reference to  FIGS. 4 and 5 , rotor assembly  108  further includes rotor biasing devices  138  coupled to and extending between rotor pins  134  and contact arm  114  to bias contact arm  114  to the first position. When contact arm  114  is in the first position, rotor biasing devices  138  maintain contact pressure and conductivity between contact arm  114  and both load strap  104  and line strap  106 . Accordingly, the repulsive forces generated by load strap  104  and line strap  106  must overcome the biasing forces of the rotor biasing devices  138  to cause contact arm  114  to move to the second position during an overcurrent condition. In the exemplary embodiment, rotor biasing devices  138  include coil springs. In alternative embodiments, rotor assembly  108  includes any rotor biasing devices  138  that enable circuit breaker  100  to operate as described herein. For example, in some embodiments, rotor assembly  108  includes a single rotor biasing device  138 . 
       FIG. 8  is a perspective view of an alternative rotor assembly  200  for circuit breaker  100 . Rotor assembly  200  includes a rotor  202 , a contact arm  204 , and a latch mechanism  206 . Rotor  202  includes a first end  208 , a second end  210 , a sidewall  212 , and rotor pins  214 . Contact arm  204  extends at least partially through openings  216  in rotor  202  and is free to move relative to rotor  202 . Rotor pins  214  extend adjacent openings  216 . In alternative embodiments, rotor  202  has any configuration that enables rotor assembly  200  to function as described herein. 
     In the exemplary embodiment, latch mechanism  206  includes a head  218  and a biasing mechanism  220 . Head  218  is movable between a neutral position and a displaced position. Biasing mechanism  220  resists displacement of head  218  and biases head  218  towards the neutral position. In the exemplary embodiment, head  218  and biasing mechanism  220  are formed by a wire partially wrapped around rotor pin  214 . In alternative embodiments, rotor assembly  200  includes any latch mechanism  206  that enables rotor assembly  200  to function as described herein. 
       FIG. 9  is a section view of an alternative circuit breaker  300  including a plurality of contact arms  302 .  FIG. 10  is a perspective view of a portion of circuit breaker  300 . Circuit breaker  300  includes a rotor assembly  304  including contact arms  302 , a rotor  306 , and a latch mechanism (not shown). Rotor  306  rotates between a closed position and a tripped or open position. In addition, contact arms  302  are movable between a first position contacting a stationary contact (not shown) and a second position spaced from the stationary contact during a high fault current event. The latch mechanism (not shown) engages contact arms  302  to retain contact arms  302  in the second position when rotor  306  is in the neutral position. The latch mechanism (not shown) is similar to latch mechanism  126  of circuit breaker  100 . Latch mechanism (not shown) engages each contact arm of circuit breaker  300 . In the illustrated embodiment, circuit breaker  300  includes five contact arms  302  positioned alongside each other. In alternative embodiments, circuit breaker  300  includes any contact arms  302  and latch mechanisms that enable circuit breaker  300  to operate as described herein. For example, in some embodiments, circuit breaker  300  includes separate latch mechanisms engaging one or more contact arms  302 . In further embodiments, circuit breaker  300  includes a latch mechanism including a plurality of heads and/or biasing mechanisms to enable the latch mechanism to engage a plurality of contact arms  302 . 
       FIG. 11  is a graph showing torque profiles of rotor assemblies.  FIG. 11  includes an X-axis defining angular position in degrees and a Y-axis defining torque in Newton-meters (Nm). The graph further includes a first curve  400 , a second curve  402 , and a third curve  404 . First curve  400  illustrates torque required to position a contact arm without engaging a retaining system. First curve  400  includes a forward motion segment  406  and a reverse motion segment  408 . Forward motion segment  406  and reverse motion segment  408  are substantially similar, with minor differences due to friction. In addition, first curve  400  is substantially constant because an approximately equal force is required to position the contact arm throughout the range of motion. Second curve  402  illustrates torque required to position a contact arm and engage a detent retaining system during a short circuit event. Second curve  402  includes a forward motion segment  410  and a reverse motion segment  412 . Forward motion segment  410  has a peak  414  representing the torque required to engage the detent system. Reverse motion segment  412  has a valley  416  representing the torque required to disengage the detent system. 
     Third curve  404  illustrates torque required to position contact arm  114  and engage latch mechanism  126 . Third curve  404  includes a forward motion segment  418  and a reverse motion segment  420 . Forward motion segment  418  has a peak  422  representing the torque required to engage latch mechanism  126 . Reverse motion segment  420  has a valley  424  representing the torque required to disengage latch mechanism  126 . Notably, peak  422  is less than peak  414  because a reduced amount of energy is required to engage latch mechanism  126  compared to the detent system. As a result, latch mechanism  126  engages contact arm  114  during short circuit event at faster time compared to the detent system. For example, opening of the contact arm of the detent system is slowed due to peak  414 . In addition, valley  424  has a greater magnitude than valley  416  because an increased amount of energy is required to disengage latch mechanism  126  compared to the detent systems. As a result, latch mechanism  126  better retains contact arm  114  in an open position and resists greater forces than detent systems. 
     In reference to  FIGS. 1-3 , a method of manufacturing circuit breaker  100  includes coupling load strap  104  and line strap  106  to case  102 . The method also includes coupling rotor  112  to case  102  such that rotor  112  is rotatable relative to case  102 . Operating mechanism  110  is coupled to rotor  112  such that operating mechanism  110  causes rotor  112  to rotate upon actuation of operating mechanism  110 . Contact arm  114  is coupled to rotor  112  such that contact arm  114  is movable between a first position where contact arm  114  engages load strap  104  and line strap  106  and a second position where contact arm  114  is disengaged from load strap  104  and line strap  106 . The method further includes coupling latch mechanism  126  to rotor  112  to inhibit movement of contact arm  114  when contact arm  114  moves to the second position without rotation of rotor  112  during a short circuit event. Latch mechanism  126  is positioned such that latch mechanism  126  is spaced from contact arm  114  when contact arm  114  is in the first position and engages contact arm  114  when contact arm  114  moves to the second position without rotation of rotor  112 . In some embodiments, head  140  of latch mechanism  126  is positioned to engage contact arm  114  when contact arm  114  moves to the second position without rotation of rotor  112 . In further embodiments, biasing mechanism  142  extends between head  140  and rotor  112  to bias head  140  towards the neutral position. 
     The circuit breakers described above generally include a contact arm that moves between a first position engaged with a stationary contact and a second position disengaged from the stationary contact. In some embodiments, the movable contact is retained in the second position by a latch mechanism. In particular, the latch mechanism is spaced from the contact arm when the contact arm is in the first position and the latch mechanism engages the contact arm when the contact arm moves to the second position without rotation of a rotor. 
     An exemplary technical effect of the methods, systems, and apparatus described herein includes at least one of: (a) reducing force required to trip circuit breakers; (b) improving interruption of high fault current using a movable contact arm; (c) reducing cost and time required to manufacture circuit breakers; (d) increasing operating efficiency of circuit breakers; (e) reducing the size of circuit breakers; ( 0  decreasing response time of circuit breakers to a short-circuit current; and (g) reducing damage to machines and equipment on a circuit protected by circuit breakers. 
     Exemplary embodiments of circuit breakers and methods of manufacturing circuit breakers are described above in detail. The circuit breakers and methods are not limited to the specific embodiments described herein but, rather, components of the circuit breakers and/or operations of the methods may be utilized independently and separately from other components and/or operations described herein. Further, the described components and/or operations may also be defined in, or used in combination with, other systems, methods, and/or devices, and are not limited to practice with only the circuit beakers and systems described herein. 
     The order of execution or performance of the operations in the embodiments of the disclosure illustrated and described herein is not essential, unless otherwise specified. That is, the operations may be performed in any order, unless otherwise specified, and embodiments of the disclosure may include additional or fewer operations than those disclosed herein. For example, it is contemplated that executing or performing a particular operation before, contemporaneously with, or after another operation is within the scope of aspects of the disclosure. 
     Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     This written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.