Patent Document

BACKGROUND OF INVENTION  
         [0001]    The present invention is directed to circuit breakers, and more particularly to interlock mechanisms to trip the circuit breaker when an electronic trip unit is separated therefrom.  
           [0002]    Circuit breakers include movable and fixed contacts for opening and closing the distribution circuit and an operating handle for manually operating the contacts. Modern industrial circuit breakers are normally provided with an electronic trip unit that electronically monitors the current levels in the circuit and trips the circuit breaker in response to a detected fault condition. Sometimes, it is convenient or necessary to remove or replace the electronic trip unit. Removing the electronic trip unit while the contacts are closed creates an obvious safety risk. Therefore, it is desirable to provide some means for preventing the contacts from being closed when the trip unit is not installed in the circuit breaker, and for causing the circuit breaker to trip, thereby separating the contacts, upon removal of the trip unit from the circuit breaker.  
           [0003]    Prior art circuit breakers having removable trip units have a portion of the main operating mechanism built into the trip unit such that when the trip unit is removed, part of the operating mechanism is also removed, making it impossible to close the main contacts. This technique increases the complexity of installation and removal of the electronic trip unit, and the expense of the trip unit. Furthermore, electronic trip units must be manufactured particularly for each model of circuit breaker.  
         SUMMARY OF INVENTION  
         [0004]    The above discussed and other drawbacks and deficiencies are overcome or alleviated by an operating mechanism for a circuit breaker. The operating mechanism comprises an operating handle movable between on and off positions extending substantially up at a point between the on and off positions; a crank for controlling a contact arm of the circuit breaker to cause the contact arm to move between open and closed positions; mechanism spring connected between the operating handle and the crank, causing said crank to move when discharged and when the operating handle is moved between said on and off positions; a trip latch configured to restrain the mechanism spring from discharging unless moved; and means for moving the trip latch upon removal of an electronic trip unit.  
           [0005]    The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0006]    Referring to the Figures wherein like elements are numbered alike in the several Figures  
         [0007]    [0007]FIG. 1 is an isometric view of an industrial-rated molded case circuit breaker;  
         [0008]    [0008]FIG. 2 is an exploded view of the circuit breaker of FIG. 1;  
         [0009]    [0009]FIG. 3 is a side view of a rotary contact assembly in an “off” condition;  
         [0010]    [0010]FIG. 4 is a side view of a rotary contact assembly in an “on” condition;  
         [0011]    [0011]FIG. 5 is a side view of a rotary contact assembly in a “tripped” condition;  
         [0012]    [0012]FIG. 6 is a perspective view of an operating mechanism;  
         [0013]    [0013]FIG. 7 is a partially exploded perspective view of the operating mechanism of FIG. 6;  
         [0014]    [0014]FIG. 8 is a partially exploded perspective view of the operating mechanism of FIG. 6;  
         [0015]    [0015]FIG. 9 is a partially exploded perspective view of a portion of the operating mechanism of FIG. 6 including a pair of mechanism springs;  
         [0016]    [0016]FIG. 10 is an exploded perspective view of a cradle from the operating mechanism of FIG. 6;  
         [0017]    [0017]FIG. 11 is a perspective view of the cradle of FIG. 10;  
         [0018]    [0018]FIG. 12 is partially exploded view of an operating mechanism and electronic trip unit interlock;  
         [0019]    [0019]FIG. 13 is a perspective view of the operating mechanism of FIG. 6, with the trip unit interlock installed thereon;  
         [0020]    [0020]FIG. 14 is a top view of internal parts of the circuit breaker of FIG. 1 with the trip unit interlock installed;  
         [0021]    [0021]FIG. 15 is a partially-assembled view of the circuit breaker of FIG. 1 showing interaction between the electronic trip unit and interlock mechanism;  
         [0022]    [0022]FIG. 16 shows the circuit breaker of FIG. 1, with the top cover lifted;  
         [0023]    [0023]FIG. 17 is close up view of a portion of FIG. 16; and  
         [0024]    [0024]FIG. 18 is a profile view of the operating and trip unit interlock mechanisms. 
     
    
     DETAILED DESCRIPTION  
       [0025]    [0025]FIG. 1 shows a circuit breaker  20 . Circuit breaker  20  generally includes a molded case having a top cover  22  attached to a mid cover  24  coupled to a base  26 .  
         [0026]    [0026]FIG. 2 shows an exploded diagram of circuit breaker  20 , showing the internal construction thereof. An opening  28 , formed generally centrally within top cover  22 , is positioned to mate with a corresponding mid cover opening  30 , which is accordingly aligned with opening  28  when mid cover  24  and top cover  22  are coupled to one another. Electronic trip unit  23  is removably positioned within top cover  22  as shown.  
         [0027]    In a 3-pole system (i.e., corresponding with three phases of current), three rotary cassettes  32 ,  34  and  36  are disposed within base  26 . Cassettes  32 ,  34  and  36  are commonly operated by an interface between an operating mechanism  38  via a cross pin  40 . Operating mechanism  38  is positioned and configured atop cassette  34 , which is generally disposed intermediate to cassettes  32  and  36 . Operating mechanism  38  operates substantially as described herein and as described in U.S. Pat. No. 6,087,913 entitled “Circuit Breaker Mechanism for a Rotary Contact Assembly”.  
         [0028]    An operating handle  44  extends through openings  28  and  30  and allows for external operation of cassettes  32 ,  34  and  36 . Examples of rotary contact structures that may be operated by operating mechanism  38  are described in more detail in U.S. Pat. Nos. 6,114,641 and 09/384,908 (GE Docket Number 41PR7613/7619), both entitled “Rotary Contact Assembly For High-Ampere Rated Circuit Breakers”, and U.S. Pat. No. 6,175,288 entitled “Supplemental Trip Unit For Rotary Circuit Interrupters”. Cassettes  32 ,  34 ,  36  are typically formed of high strength plastic material and each include opposing sidewalls  46 ,  48 . Sidewalls  46 ,  48  have an arcuate slot  52  positioned and configured to receive and allow the motion of cross pins  40  by action of operating mechanism  38 .  
         [0029]    Referring now to FIGS. 3, 4, and  5 , an exemplary rotary contact assembly  56  that is disposed within each cassette  32 ,  34 ,  36  is shown in the “off”, “on” and “tripped” conditions, respectively. Also depicted are partial side views of operating mechanism  38 , the components of which are described in greater detail further herein. Rotary contact assembly  56  includes a load side contact strap  58  and line side contact strap  62  for connection to a power source and a protected circuit (not shown), respectively. Load side contact strap  58  includes a stationary contact  64  and line side contact strap  62  includes a stationary contact  66 . Rotary contact assembly  56  further includes a movable contact arm  68  having a set of contacts  72  and  74  that mate with stationary contacts  64  and  66 , respectively. In the “off” position (FIG. 3) of operating mechanism  38 , wherein operating handle  44  is oriented to the left (e.g., via a manual or mechanical force), contacts  72  and  74  are separated from stationary contacts  64  and  66 , thereby preventing current from flowing through contact arm  68 . It should be appreciated that while rotary contact assembly  56  shows a contact arm having a pair of movable contacts, rotary contact assemblies wherein the contact arm has only a single movable contact is contemplated.  
         [0030]    In the “on” position of operating mechanism  38  shown in FIG. 4, wherein operating handle  44  is oriented to the right as depicted in FIG. 4 (e.g., via a manual or mechanical force), contacts  72  and  74  are mated with stationary contacts  64  and  66 , thereby allowing current to flow through contact arm  68 . In the “tripped” position shown in FIG. 5, operating handle  44  is oriented between the “on” position and the “off” positions (typically by the release of mechanism springs within operating mechanism  38 , described in greater detail herein). In this “tripped” position, contacts  72  and  74  are separated from stationary contacts  64  and  66  by the action of operating mechanism  38 , thereby preventing current from flowing through contact arm  68 . After operating mechanism  38  is in the “tripped” position, it must ultimately be returned to the “on” position for operation. This is effectuated by applying a reset force to move operating handle  44  to a “reset” condition, which is beyond the “off” position (i.e., further to the left of the “off” position in FIG. 3), and then back to the “on” position. This reset force must be high enough to overcome the mechanism springs, described herein.  
         [0031]    Contact arm  68  is mounted on a rotor structure  76  that houses one or more sets of contact springs. Contact arm  68  and rotor structure  76  pivot about a common center  78 . Cross pin  40  interfaces through an opening  82  within rotor structure  76  generally to cause contact arm  68  to be moved from the “on”, “off” and “tripped” position.  
         [0032]    Referring now to FIGS.  6 - 8 , the components of operating mechanism  38  will now be detailed. As viewed in FIGS.  6 - 8 , operating mechanism  38  is in the “tripped” position. Operating mechanism  38  has operating mechanism side frames  86  configured and positioned to straddle sidewalls  46 ,  48  of cassette  34  (FIG. 2).  
         [0033]    Operating handle  44  (FIGS.  2 - 4 ) is rigidly interconnected with a drive member or handle yoke  88 . Handle yoke  88  includes opposing side portions  89 . Each side portion  89  includes an extension  91  at the top of side portion  89 , and a U-shaped portion  92  at the bottom portion of each side portion  89 . U-shaped portions  92  are rotatably positioned on a pair of bearing portions  94  protruding outwardly from side frames  86 . Bearing portions  94  are configured to retain handle yoke  88 , for example, with a securement washer. Handle yoke  88  further includes a roller pin  114  extending between extensions  91 .  
         [0034]    Handle yoke  88  is connected to a set of powerful mechanism springs  96  by a spring anchor  98 , which is generally supported within a pair of openings  102  in handle yoke  88  and arranged through a complementary set of openings  104  on the top portion of mechanism springs  96 .  
         [0035]    Referring to FIG. 9, the bottom portion of mechanism springs  96  include a pair of openings  206 . A drive connector  201235  operatively couples mechanism springs  96  to other operating mechanism components. Drive connector  201235  comprises a pin  202  disposed through openings  206 , a set of side tubes  203  arranged on pin  202  adjacent to the outside surface of the bottom portion of mechanism springs  96 , and a central tube  204  arranged on pin  202  between the inside surfaces of the bottom portions of mechanism springs  96 . Central tube  204  includes step portions at each end, generally configured to maintain a suitable distance between mechanism springs  96 . While drive connector  201235  is detailed herein as tubes  203 ,  204  and a pin  202 , any means to connect the springs to the mechanism components are contemplated.  
         [0036]    Referring to FIGS. 8, 10, and  11 , a pair of cradles  106  are disposed adjacent to side frames  86  and pivot on a pin  108  disposed through an opening  112  approximately at the end of each cradle  106 . Each cradle  106  includes an edge surface  107 , an arm  122  depending downwardly, and a cradle latch surface  164  above arm  122 . Edge surface  107  is positioned generally at the portion of cradle  106  in the range of contact with roller pin  114 . Each cradle  106  also includes a stop surface  110  formed thereon. A rivet  116  disposed through an arcuate slot  118  within each side frame  86 , as best seen in FIGS. 5 and 8, guides the movement of each cradle  106 . Rivets  116  are disposed within an opening  117  on each cradle  106  (FIG. 11). An arcuate slot  168  is positioned intermediate to opening  112  and opening  117  on each cradle  106 . An opening  172  is positioned above slot  168 .  
         [0037]    Referring back to FIGS.  6 - 8 , a primary latch  126  is positioned within side frames  86 . Primary latch  126  includes a pair of side portions  128  (FIG. 8). Each side portion  128  includes a bent leg  124  at the lower portion thereof. Side portions  128  are interconnected by a central portion  132 . A set of extensions  166  depend outwardly from central portion  132  positioned to align with cradle latch surfaces  164 .  
         [0038]    Side portions  128  each include an opening  134  positioned so that primary latch  126  is rotatably disposed on a pin  136 . Pin  136  is secured to each side frame  86 . A set of upper side portions  156  are defined at the top end of side portions  128 . Each upper side portion  156  has a primary latch surface  158 .  
         [0039]    A secondary latch  138  is pivotally straddled over side frames  86 . Secondary latch  138  includes a set of pins  142  disposed in a complementary pair of notches  144  on each side frame  86 . Secondary latch  138  includes legs  139  each having a secondary latch trip tab  146  that extends perpendicularly from operating mechanism  38 . Secondary latch  138  includes a set of latch surfaces  162 , that align with primary latch surfaces  158 .  
         [0040]    Secondary latch  138  is biased in the clockwise direction due to the pulling forces of a spring  148  (FIG. 8). Spring  148  has a first end connected at an opening  152  upon secondary latch  138 , and a second end connected at a frame cross pin  154  disposed between frames  86 .  
         [0041]    A set of upper links  174  are connected to cradles  106 . Upper links  174  generally have a right angle shape, as best viewed in FIGS. 8 and 10. Legs  175  (in a substantially horizontal configuration in FIG. 10) of upper links  174  each have a cam surface  171  that interfaces a roller  173  disposed between frames  86  (FIG. 8). Legs  176  (in a substantially vertical configuration in FIGS. 8 and 10) of upper links  174  each have a pair of openings  182 ,  184  and a U-shaped portion  186  at the bottom end thereof. Opening  184  is intermediate to opening  182  and U-shaped portion  186 . Upper links  174  connect to cradle  106  via a securement structure such as a rivet pin  188  disposed through opening  172  and opening  182 , and a securement structure such as a rivet pin  191  disposed through slot  168  and opening  184 . Rivet pins  188 ,  191  (FIG. 11) both attach to a connector  193  to secure each upper link  174  to each cradle  106 . Each pin  188 ,  191  includes raised portions  189 ,  192 , respectively. Raised portions  189 ,  192  are provided to maintain a space between each upper link  174  and each cradle  106 . The space serves to reduce or eliminate friction between upper link  174  and cradle  106  during any operating mechanism motion, and also to spread force loading between cradles  106  and upper links  174 .  
         [0042]    Upper links  174  are each interconnected with a lower link  194 . Referring now to FIGS. 8 and 9, U-shaped portion  186  of each upper link  174  is disposed in a complementary set of bearing washers  196 . Bearing washers  196  are arranged on each side tube  203 . Bearing washers  196  are configured to include side walls spaced apart sufficiently so that U-shaped portions  186  of upper links  174  fit in bearing washer  196 . Pin  202  is disposed through side tubes  203  and central tube  204 . Pin  202  interfaces upper links  174  and lower links  194  via side tubes  203 . Therefore, each side tube  203  is a common interface point for upper link  174  (as pivotally seated within side walls of bearing washer  196 ), lower link  194  and mechanism springs  96 .  
         [0043]    Each lower link  194  is interconnected with a crank  208  via a pivotal rivet  210 . Each crank  208  pivots about a center  211  . Crank  208  has an opening  212  where cross pin  40  (FIG. 2) passes through into arcuate slot  52  of cassettes  32 ,  34  and  36  and a complementary set of arcuate slots  214  on each side frame  86  (FIG. 8).  
         [0044]    A spacer  234  is included on each pivotal rivet  210  between each lower link  194  and crank  208 . Spacers  234  spread the force loading from lower links  194  to cranks  208  over a wider base, and also reduces friction between lower links  194  and cranks  208 , thereby minimizing the likelihood of binding (e.g., when operating mechanism  38  is changed from the “off” position to the “on” position manually or mechanically, or when operating mechanism  38  is changed from the “on” position to the “tripped” position of the release of primary latch  126  and secondary latch  138 ).  
         [0045]    Referring back to FIGS.  3 - 5 , the movement of operating mechanism  38  relative to rotary contact assembly  56  will be detailed.  
         [0046]    Referring to FIG. 3, in the “off” position operating handle  44  is rotated to the left and mechanism springs  96 , lower link  194  and crank  208  are positioned to maintain contact arm  68  so that movable contacts  72 ,  74  remain separated from stationary contacts  64 ,  66 . Operating mechanism  38  becomes set in the “off” position after a reset force properly aligns primary latch  126 , secondary latch  138  and cradle  106  (e.g., after operating mechanism  38  has been tripped) and is released. Thus, when the reset force is released, extensions  166  of primary latch  126  rest upon cradle latch surfaces  164 , and primary latch surfaces  158  rest upon secondary latch surfaces  162 . Each upper link  174  and lower link  194  are bent with respect to each side tube  203 . The line of forces generated by mechanism springs  96  (i.e., between spring anchor  98  and pin  202 ) is to the left of bearing portion  94  (as oriented in FIGS.  3 - 5 ). Cam surface  171  of upper link  174  is out of contact with roller  173 .  
         [0047]    Referring now to FIG. 4, a manual closing force was applied to operating handle  44  to move it from the “off” position (i.e., FIG. 4) to the “on” position (i.e., to the right as oriented in FIG. 5). While the closing force is applied, upper links  174  rotate within arcuate slots  168  of cradles  106  about pins  188 , and lower link  194  is driven to the right under bias of the mechanism spring  96 . Side walls of bearing washers  196  maintain the position of upper link  174  on side tube  203  and minimize likelihood of binding (e.g., so as to prevent upper link  174  from shifting into springs  96  or into lower link  194 ).  
         [0048]    To align vertical leg  176  and lower link  194 , the line of force generated by mechanism springs  96  is shifted to the right of bearing portion  94 , which causes rivet  210  coupling lower link  194  and crank  208  to be driven downwardly and to rotate crank  208  clockwise about center  211 . This, in turn, drives cross pin  40  to the upper end of arcuate slot  214 . Therefore, the forces transmitted through cross pin  40  to rotary contact assembly  56  via opening  82  drive movable contacts  72 ,  74  into stationary contacts  64 ,  66 .  
         [0049]    The interface between primary latch  126  and secondary latch  138  (i.e., between primary latch surface  158  and secondary latch surface  162 ), and between cradles  106  and primary latch  126  (i.e., between extensions  166  and cradle latch surfaces  164 ) is not affected when a force is applied to operating handle  44  to change from the “off” position to the “on” position.  
         [0050]    Referring again to FIG. 5, in the “tripped” condition, secondary latch trip tab  146  has been displaced, e.g., by electronic trip unit interlock, described in detail below, and the interface between primary latch  126  and secondary latch  138  is released. Extensions  166  of primary latch  126  are disengaged from cradle latch surfaces  164 , and cradles  106  is rotated clockwise about pin  108  (i.e., motion guided by rivet  116  in arcuate slot  118 ). The movement of cradle  106  transmits a force via rivets  188 ,  191  to upper link  174  having cam surface  171 . After a short predetermined rotation, cam surface  171  of upper link  174  contacts roller  173 . The force resulting from the contact of cam surface  171  on roller  173  causes upper link  174  and lower link  194  to buckle and allows mechanism springs  96  to pull lower link  194  via pin  202 . In turn, lower link  194  transmits a force to crank  208  (i.e., via rivet  210 ) causing crank  208  to rotate counter clockwise about center  211  and drive cross pin  40  to the lower portion of arcuate slot  214 . The forces transmitted through cross pin  40  to rotary contact assembly  56  via opening  82  cause movable contacts  72 ,  74  to separate from stationary contacts  64 ,  66 .  
         [0051]    Referring now to FIGS.  12 - 18 , the electronic trip unit interlock mechanism will be described in detail. FIGS. 12 and 13 show isometric views of circuit breaker  20  rotated approximately 180 degrees about a central axis relative to FIG. 1. FIG. 12 shows the components of the electronic trip unit interlock are separated from the operating mechanism and FIG. 13 shows the components installed. In each of FIGS. 12 and 13, the top cover  22 , mid cover  24 , and base  26  removed and the outside cassette  36  is not shown for clarity. The trip arm  253  is mounted to the side of operating mechanism  38  as shown and rotates about a fixed pivot  254 . Trip arm  253  includes a leg  257  having a first surface in contact with trip plunger  275  and an extension  270  having a latch surface for contacting secondary trip latch  138 . Extension bar  255  is positioned between operating mechanism  38  and breaker load vent assembly  267 . Extension bar includes a finger  259  having a first surface that comes into contact with electronic trip unit  23  when it is installed, and a nub  258  having a second surface in contact with trip plunger  275 . Center barrier  268  contains a bored hole  271  located as shown. Trip spring  274  and trip plunger  275  are positioned within hole  271 . FIG. 13 shows the trip plunger  275  positioned under leg  257  of trip arm  253 .  
         [0052]    [0052]FIG. 14 shows extension bar  255  as it interacts with trip plunger  275 . When extension bar  255  is in the position shown, it holds trip plunger  275  in its depressed position away from leg  257  of trip arm  253 . When extension bar  255  is allowed to move, to the position shown in phantom in FIG. 14, it allows trip plunger  275  to be driven in an upwards direction by trip spring  274  into an interference with leg  257  of trip lever  253 . Extension bar  255  is held in the position which depresses trip plunger  275  when the electronic trip unit  23  is installed in circuit breaker  20  as shown in FIG. 15. When electronic trip unit  23  is removed, extension bar  255  is released, allowing trip plunger  275  to move in an upwards direction, moving extension bar  255  to the phantom position shown in FIG. 14.  
         [0053]    [0053]FIG. 16 clarifies the relationship between finger  259  of extension bar  255  as it relates to mid cover  24  and electronic trip unit  23 . FIG. 17 shows a detail of a portion  217  of FIG. 16, showing finger  259  extending up from mid cover  24 .  
         [0054]    Referring now to FIG. 18, in response to electronic trip unit  23  being removed, spring  274  has urged plunger  275  in an upward direction, causing extension bar  255  to move up and trip arm  253  to rotate in a counter-clockwise direction about pivot  254 . Extension  270  of trip arm  253  includes a latch surface that interacts with secondary latch trip tab  146  of secondary latch  138 . In response to this interaction, secondary latch  138  is caused to rotate in a clockwise direction about pins  142 , causing the operating mechanism to trip as previously described, separating movable contacts  74 ,  72  from fixed contacts  66 ,  64 . Unless electronic trip unit  23  is replaced, the operating mechanism will remain in this position and will not allow the main contacts to be closed.  
         [0055]    When trip unit  23  is replaced as shown in FIG. 15, surface  260  interacts with finger  259  of extension bar  255 , forcing extension bar  255  to rotate downwardly. When extension bar is forced down, nub  258  forces plunger  275  to become depressed, as shown in FIG. 14. In response to plunger  275  being depressed, trip arm  253  is permitted to rotate clockwise about pivot  254 . Spring  265  (FIGS. 13, 18) urges trip arm  253  to rotate in a clockwise direction, thus causing trip arm  253  to rotate in a clockwise direction when free to do so.  
         [0056]    While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. For example, trip arm  253  may be mounted and configured to slide instead of rotate, and/or may engage an intermediary which then actuates secondary trip latch  138 , rather than actuating secondary trip latch  138  directly. Additionally, electronic trip unit  23  may engage a surface of trip arm  253  or other intermediary rather than work directly against plunger  275 . These and other modifications would occur to the skilled artisan to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Technology Category: 5