Abstract:
An auxiliary switch for a circuit breaker of the split case type. The switch is capable of switching the rated interrupt current capacity of the breaker and is fitted in to the circuit breaker case so that the overall width is substantially equal to or less than the overall width of the circuit breaker. Several embodiments of the auxiliary switch disclose various features which contribute to increasing the interrupt current rating and/or down sizing the width of the auxiliary switch. Among them are: an early make, late break of the auxiliary contacts compared to the circuit breaker contacts; an inertia dampening fly wheel attached to the actuator of the switch to enhance the early make/late break feature; a wiping action between the moveable and stationary contacts of the auxiliary switch to clean off welding and debris deposited from arcing; dual auxiliary contacts to enhance the contact area with little impact on package size and width; and a positioning of the auxiliary actuator on the contact lever of the circuit breaker to prevent the spring forces acting on the actuator from affecting circuit breaker contact pressure.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to circuit breakers. More specifically, the present invention relates to an auxiliary switch for a circuit breaker which is capable of switching substantially the rated interrupt current of the circuit breaker. 
     BACKGROUND OF THE INVENTION 
     Control panel systems, having a variety of panel mounted circuit breakers mounted thereon, are often sold in both the United States and Europe to provide branch circuit protection or supplementary (equipment) protection. By way of example, circuit breakers are often mounted in theater lighting control panel systems to provide protection for branch circuits which supply electrical power to the various lights of a theater. Alternatively, circuit breakers can also be mounted in control panels to provide dedicated supplementary protection to equipment such as computers, power supplies or copying machines. 
     Circuit protection standards vary between the United States and Europe, and impose different performance requirements on the circuit breakers involved. For example, U.S. standards rarely allow the provision of a disconnect to the neutral (return) side of a circuit load, while European standards often require it. European standards for a neutral disconnect effectively requires the addition of another switch, capable of handling the rated interrupt current capacity of the circuit breaker, when connected in series with the circuit breaker and the load. Rated interrupt current, i.e., interrupting rating, is defined in article 100 of the 1996 edition of the National Electric Code, published by the National Fire Protection Association, Quincy, Mass., as: “the highest current at rated voltage that a device is intended to interrupt under standard test conditions”. The interrupt current and the standard test conditions for a device, such as a circuit breaker, would typically be specified in an industry excepted standard, e.g., UL 1077, titled Standard For Supplementary Protectors For Use In Electrical Equipment, or UL489, titled Standard For Molded Case Circuit Breakers And Circuit Breaker Enclosures. Prior art attempts to modify existing U.S. circuit breakers to provide neutral side disconnects involved stacking a second pole up against the single pole circuit breaker, effectively doubling the width and size of such an assembly. 
     However, space is a premium in control panel systems. In the telecommunication industry, for example, telecommunication equipment designers can earn bonuses of up to $1000 for every square inch of panel space saved. Consequently, there is often very little panel space to accommodate the additional second pole for the circuit breakers without an expensive redesign of the system. This is especially critical when the additional requirements increase the overall package width, since the circuit breakers are often stacked side by side, leaving very little space in between for growth. 
     Auxiliary switches are often mounted to the bottom portions of circuit breakers to provide an extra set of switching contacts without a significant increase in overall package size or width. However, auxiliary switches are primarily used to indicate status of the circuit breaker, e.g., whether the circuit breaker is open or closed, and typically have current switching capacities which are much lower than the interrupt current capacity rating of the main breaker. The low power auxiliary switches are constructed of much smaller components and require much less space to actuate than the main contacts of the circuit breaker. 
     To construct an auxiliary switch capable of switching the rated interrupt current capacity of its associated circuit breaker with a minimum impact in overall package width is problematic for several reasons. For example, the contact gap spaces and spring forces for the auxiliary switch must increase, tending to increase the package size and width. Also, since the auxiliary contacts are mechanically actuated by the main breaker contacts, the increased spring forces from the auxiliary switch actuator acting on the main breaker contacts may significantly change the main breaker contact pressure. This can result in excessive arcing and premature circuit breaker contact wear. 
     Another significant factor which tends to make the auxiliary switch package grow is that the higher power requirements can result in greater arcing during make (make contact) or break (break contact) of the auxiliary contacts. This increases the possibility of welding the contacts together or leaving debris and carbon deposits on the contacts. This problem is often minimized in the main circuit breaker with a lateral wiping action designed between the movable and stationary contacts of the main breaker. The wiping action is used to clean the contacts and shear away any welds as the contacts make or break. That is, the moveable contacts of the main circuit breaker pivots on a moveable contact lever to make contact with the stationary contact. A generally kidney shaped slot at the pivot point of the movable contact lever is fundamental to this arcuate motion. This slot is easily elongated to provide for over travel in the lateral directions of the contacts relative to each other, which results in the wiping action. 
     However, auxiliary switch contacts are typically designed to have a substantially linear motion when bridging the contact gaps (bridge contacts), rather than the arcuate motion described above for the main breaker contacts. Problematically, the bridge contacts are not conducive to providing a wiping action in the lateral direction. The arcing problem can be compensated for by increasing the size of the auxiliary contacts and their associated contact gaps, but this tends to unduly increase the overall package size and width. 
     Accordingly, there is a need for an improved auxiliary switch for a circuit breaker, which is capable of switching the rated interrupt current capacity of the associated circuit breaker. 
     SUMMARY OF THE INVENTION 
     The present invention offers advantages and alternative over the prior art by providing an auxiliary switch for a circuit breaker capable of switching the rated interrupt current capacity of the breaker. The auxiliary switch/circuit breaker assembly can be used to provide neutral disconnects to an existing control panel system to meet European standards. 
     These and other advantages are accomplished in an exemplary embodiment of the invention by providing a circuit breaker assembly comprising a circuit breaker and an auxiliary switch. The circuit breaker has a predetermined rated interrupt current capacity, and includes a movable contact lever having a circuit breaker moveable contact disposed thereon. The contact lever has an open position and a closed position. The auxiliary switch includes a switch housing mounted in an opening defined by the circuit breaker. An auxiliary actuator is movably mounted within the switch housing and has an upper portion of the auxiliary actuator protruding into the opening of the circuit breaker from the switch housing. An auxiliary moveable contact member has an auxiliary moveable contact disposed thereon, the member is moveably mounted to the auxiliary actuator. A contact spring acts between the auxiliary actuator and the auxiliary moveable contact member. An auxiliary stationary contact is arranged in the switch housing for engagement with the auxiliary moveable contact. A return spring is disposed between the switch housing and auxiliary actuator urging the auxiliary stationary and moveable contacts apart. The auxiliary switch is adapted to switch substantially the rated interrupt current of the circuit breaker through the moveable and stationary auxiliary contacts when the moveable contact lever of the circuit breaker moves from the open position to the close position, thereby depressing the auxiliary actuator to have the auxiliary moveable contact make contact with the auxiliary stationary contact. 
     In an alternative embodiment of the invention the overall width of the auxiliary switch is substantially equal to or less than the overall width of the circuit breaker. 
     Several embodiments of the auxiliary switch disclose various features which contribute to increasing the interrupt current rating and/or down sizing the width of the auxiliary switch. Among them are: 
     an early make, late break of the auxiliary contacts compared to the circuit breaker contacts; 
     an inertia dampening fly wheel attached to the actuator of the switch to enhance the early make/late break feature; 
     a wiping action between the moveable and stationary contacts of the auxiliary switch to clean off welding and debris deposited from arcing; 
     dual auxiliary contacts to enhance the contact area with little impact on package size and width; and 
     a positioning of the auxiliary actuator on the contact lever of the circuit breaker to prevent the spring forces acting on the actuator from affecting circuit breaker contact pressure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a circuit breaker assembly in accordance with the present invention; 
     FIG. 2 is a side view of FIG. 1; 
     FIG. 3 is a perspective view of the interior of the circuit breaker assembly with the circuit breaker moveable contact lever in the open position; 
     FIG. 4 is a perspective view of the interior of the circuit breaker assembly with the circuit breaker moveable contact lever in the closed position; 
     FIG. 5 is a perspective view of an embodiment of the auxiliary switch showing an inertia dampening fly wheel in accordance with the present invention; 
     FIG. 6 is a perspective view of an embodiment of the auxiliary switch showing a canted moveable contact member in accordance with the present invention; 
     FIG. 7 is a side view of the actuator of the switch in FIG. 6; 
     FIG. 8 is an enlarged view of the moveable and stationary contact of the auxiliary switch of FIG. 6 with their centerlines offset; 
     FIG. 9 is an enlarged view of the moveable and stationary contact of the auxiliary switch of FIG. 6 with their centerlines aligned; 
     FIG. 10 is a force balance diagram on the moveable contact lever of the circuit breaker of FIG. 4 in the closed position; 
     FIG. 11 is a schematic diagram of the auxiliary switch contacts having a single pole, single throw, double break arrangement; 
     FIG. 12 is a schematic diagram of the auxiliary switch contacts having a single pole, double throw, double break arrangement; 
     FIG. 13 is a wiring diagram of the auxiliary switch used as a neutral disconnect with the circuit breaker; and 
     FIG. 14 is a wiring diagram of the auxiliary switch wired in series with the circuit breaker to increase interrupt capability of the circuit breaker in a DC circuit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, front and side views respectively, of an exemplary embodiment of a circuit breaker assembly in accordance with the present invention is shown generally at  10 . The circuit breaker assembly  10  includes a circuit breaker  12  with an auxiliary switch  14  mounted thereon. Half shells  16  and  18  form a split case enclosure  20  which encloses the interior components of the circuit breaker  12 . Toggle handle  22 , extending out of the top of circuit breaker  12 , is pivotally mounted to the interior of the split case  20  to provide manual actuation of the circuit breaker  12 , and circuit breaker terminals  24  and  26 , extending through the bottom of circuit breaker  20 , provide electrical connection to load and source lines (not shown). The auxiliary switch  14  includes a switch housing  28  mounted in an opening defined by the circuit breaker  12 , and has a pair of auxiliary terminals  30  and  32  extending straight through the bottom of switch housing  28 . The auxiliary terminals include a center hole  33  through which a wire, e.g., a source line or load line, can be attached. 
     As will be discussed in greater detail hereinafter, the auxiliary switch  14  is adapted to switch substantially the rated interrupt current of circuit breaker  12  without substantially changing the overall package width of the circuit breaker assembly  10 . That is the overall width of the auxiliary switch  14  is substantially equal to or less than the overall width of the circuit breaker  12 . 
     Typically, the auxiliary switch  14  and circuit breaker  12  fall into a general industry classification of “Low Voltage” circuit protection devices, which have normal operation ratings that range up to 100 amps at 300 volts AC or 100 amps at 80 volts DC. In addition to the normal operation ratings, circuit protection devices are required to be rated for the maximum current they can safely interrupt under standard test conditions at their rated voltage. This rating is known as the interrupt current capacity of the circuit protection device. The auxiliary switch  14  is typically rated for use, in series with the circuit breaker, with an interrupt current capacity of 5000 amps at 120 volts AC, 3000 amps at 240 volts AC, and 5000 amps at 80 volts DC. 
     Comparatively, prior art auxiliary switches in these voltage ranges are not rated for handling substantially higher interrupt currents than the normal operation current ratings and are therefore limited to use for indicating circuit breaker status, e.g., on/off or make/break. 
     Though this embodiment describes a split case circuit breaker, the circuit beaker can be any switch that automatically interrupts an electric circuit under an infrequent abnormal condition, e.g., current overload. 
     Referring to FIGS. 3 and 4, the circuit breaker  12  includes a collapsible linkage assembly  34  engaged between a moveable contact lever  36  and the handle  22  which is pivotally mounted to the circuit breaker enclosure  20 . The moveable contact lever  36  includes a circuit breaker moveable contact  38  disposed thereon which traverses from an open position  40  to a closed position  42  across a predetermined first distance  43 , to make electrical contact (make) with circuit breaker stationary contact  44 . Typically, when the contact lever  36  is in the closed position, a source current will conduct through terminal  26  to the stationary contact  44 . The current is conducted through the stationary contact  44 , through the movable contact  38 , to the movable contact lever  36 . The movable contact lever  36  is connected to the current sensing electromagnetic coil  48  through lead  52 . The coil  48  is connected through lead  50  to the terminal  24  and out to a load. When the current in the coil exceeds a predetermined rated current capacity, e.g. rated operational current or rated interrupt current, the coil will cause the circuit breaker to trip, thereby collapsing the linkage assemble  34 , pivoting the moveable contact lever  36  from the closed position  42  to the open position  40  and breaking contact (break) between the moveable and stationary contacts  38  and  44  to open the circuit. An auxiliary coil  45  may be provided for allowing remote or relay opening of the contacts  42 / 44 . The auxiliary coil  45  is preferably on a separate bobbin from the main coil  48  rather than simply supplied as an alternative to the usual circuit breaker configuration with a single main coil. See U.S. Pat. No. 4,982,174 for such an arrangement. In FIGS. 3 and 4, the auxiliary coil bobbin is made in two parts so as to surround the coil  45  completely. The arrangement assures that failure of the coil  45  will not interfere with normal circuit breaker operation. 
     The auxiliary switch housing  28 , of the auxiliary switch  14 , includes flanges  54  which slidably engages circuit breaker mounting grooves  56  to mount the housing  28  into opening  58  defined by the circuit breaker enclosure  20 . The auxiliary switch  14  also includes an auxiliary actuator  60  slidably mounted within the switch housing  28 . An upper portion  62  of the auxiliary actuator  60  protrudes into the opening  58  of the circuit breaker  12  from the switch housing  28 . An auxiliary moveable contact member  64  extends laterally out of opposing sides of a hollow lower portion  66  of the auxiliary actuator  60  and has a pair of auxiliary moveable contacts  68  disposed thereon. The moveable contact member  64  is moveably mounted and retained by the hollow lower portion  66  of the auxiliary actuator  60 . A contact spring  70  (shown in dotted lines) acts between the auxiliary actuator  60  and the auxiliary moveable contact member  64  to urge the moveable contact member  64  against the bottom of the auxiliary actuator  60 . A return spring  72  is disposed between the switch housing  28  and the auxiliary actuator  60  urging the upper portion  62  of the auxiliary actuator  60  into engagement against the movable contact lever  36  of the circuit breaker  12 . A pair of auxiliary stationary contacts  74  are arranged in the switch housing  28  for engagement with the auxiliary moveable contacts  68  and are spaced a second predetermined distance  76  therefrom. When the moveable contact lever  36  of the circuit breaker  12  moves from the open position  40  to the close position  42 , the contact lever  36  depresses the auxiliary actuator  60  to have the auxiliary moveable contact  68  traverse the second predetermined distance  76  and make contact with the auxiliary stationary contact  74 . 
     Typically, when the auxiliary switch  14  is used as a neutral disconnect for a protected load, the auxiliary contacts  68  and  74  of the auxiliary switch  14  will be wired on the neutral side of the load in series with the load and the circuit breaker contacts  38  and  44  of the circuit breaker  12 . In this case, when the auxiliary contacts  68  and  74  are closed, load current will conduct from terminal  30 , through one of the moveable and stationary contacts  68  and  74 , across the moveable contact member  64 , through the other moveable and stationary contacts  68  and  74 , and out terminal  32  to the source. Since the auxiliary actuator  60  of the auxiliary switch  14  is mechanically actuated by circuit breaker contact lever  36 , when the circuit breaker  12  trips the actuator switch  14  will also trip, thereby causing the auxiliary contacts  68  and  74  to separate and disconnect the neutral line from the load. 
     By utilizing the dual pair of moveable and stationary auxiliary contacts  68  and  74  rather than a single set of contacts, the contact surface area and gap size are effectively doubled without significantly affecting the overall width of the auxiliary switch  14 . The dual contacts are therefor a contributing factor to the increased current capacity of the auxiliary switch  14 . 
     Another factor that reduces arcing in the auxiliary switch  14  and enables the auxiliary switch  14  to switch substantially the rated interrupt current of the circuit breaker  12 , is a late break, early make feature. That is, the predetermined second distance  76  through which the auxiliary moveable contacts  68  must traverse is designed to be less than the predetermined first distance  43  through which the circuit breaker moveable contact  38  must traverse. Consequently, the moveable and stationary contacts  68  and  74  of the auxiliary switch  14  will make earlier and break later, than the moveable and stationary contacts  38  and  44  of the circuit breaker  12 . Therefore, most of the arcing occurs across the larger circuit breaker contacts when they make or break first, enabling the smaller auxiliary contacts to be reduced in size for the same interrupt current rating. 
     Though the circuit breaker moveable contact lever  36  is shown as a pivotally mounted moveable contact arm, other moveable contact lever embodiments are also considered within the scope of this invention. By way of example, the lever  36  may have a dual contact bridge configuration similar to that of the moveable contact member  64 . 
     Though the auxiliary actuator  60  is shown in this embodiment as being slidably mounted within the switch housing  28 , one skilled in the art would recognize that the auxiliary actuator  60  may be moveably mounted in other ways, e.g., pivotally mounted. Additionally, though the auxiliary actuator  60  is shown in this embodiment as making contact with the moveable contact lever  36  when it is in the open position  40 , a gap may exist between the auxiliary actuator  60  and the moveable contact lever  36  when it is in this position  40 . In that case, the gap will be closed as the moveable contact lever  36  moves from the open position  40  to the closed position  41  to contact and depress the auxiliary actuator  60 . 
     Referring to FIG. 5, another embodiment of the auxiliary actuator switch  14  shows an enhancement to the early make, late break feature whereby an inertia dampening flywheel  73  is pivotally attached to the switch housing  28  via flywheel pivot axis  75 . The flywheel has an engagement slot  77  slidably engaged to a mounting pin  79  located on the lower portion  66  of the auxiliary actuator  60 . 
     The fly wheel  73  engaged with the auxiliary switch actuator  60  provides inertia dampening to the auxiliary switch  14  such that the moveable and stationary contacts  68  and  74  of the auxiliary switch  14  break later than the moveable and stationary contacts  38  and  44  of the circuit breaker  12 . When the inertia dampening of the flywheel is combined with the early make, late break design discussed previously, the arcing across the auxiliary contacts  68  and  74  is further reduced, allowing the auxiliary switch  14  to be further down sized. 
     Referring to FIGS. 6 and 7, an alternative embodiment of the auxiliary switch  14  is shown where case  28  further includes an upper portion  78  removeably attached to a lower portion  80 . The lower portion  80  covers and protects right angle terminals  82  and has lower portion hooks  84  extending upwardly to removably engage with upper portion hooks  86  extending downwardly from the bottom of the upper portion  78  of case  28 . 
     This embodiment also shows the auxiliary moveable contact member  64  canted (tilted) relative to the substantially horizontal stationary contacts  74  which enables a contact wiping action when the moveable and stationary contacts  68  and  74  make and break. The lower portion  66  of the auxiliary actuator  60  has a hollow section  88  with a canted bottom surface  89  which slidably retains the contact spring  70  and contact member  64 . The contact spring  70  urges the contact member  64  flush against the canted surface  89  when the actuator  60  is fully extended, i.e., when the moveable contact lever  38  is in the open position  40 . 
     Referring to FIGS. 8 and 9, a convex surface  90  is disposed on the auxiliary moveable contacts  68  having a centerline  92  substantially normal to the surface  90 . Additionally, a convex surface  94  is disposed on the auxiliary stationary contacts  74  having a centerline  96  substantially normal to the surface  94 , and facing the convex surface  90  of the auxiliary moveable contacts  68 . When the moveable contact lever  36  pivots from the open position  40  to the closed position  42 , the actuator  60  is depressed. The moveable and stationary contacts  68  and  74  move linearly toward each other until their convex surfaces  90  and  94  make contact with their centerlines  92  and  96  being offset. The pair of stationary contacts  74  then lift the moveable contact member  64  off of the canted surface  89  of the actuator  60  such that the contact spring  70  generates a force along the centerline  92  of the moveable contacts  68 . Consequently, a reactionary force is generated along the centerline  96  of the stationary contact  74 . This misalignment of forces creates a moment that rotates the moveable contact member  64 . Since the contact member  64  is retained by the hollow section  88  of actuator  60 , it is forced to pivot about a pivot point  98  urging the centerlines  92  and  96  of the contacts  68  and  74  substantially into alignment. This rotation causes a relative lateral motion between the moveable and stationary contacts  68  and  74 , wiping the surfaces  90  and  94  clean of welds and debris caused by arcing on break. On break, the slanted surface  89  of the actuator  60  contacts one side of the moveable contact member  64  first, generating a twisting moment that will shear any contact welds caused by arcing on make. The wiping action enables the spring forces and contact surface areas to be downsized, and therefore is an additional factor in enabling the switch to keep a small package size and a high interrupt current rating. 
     Referring to FIG. 10, a force balance diagram on the moveable contact lever  36  in the closed position  42  is shown. A toggle compression force F T  is generated by the collapsible linkage assembly  34  on the contact lever  36 . The toggle compression force F T  has a line of direction which passes through toggle attachment point  100  and fulcrum point  101  which is located on the moveable contact  38  side of the moveable contact lever  36 . A main spring force F MS  through the main spring pin  102  reacts to the toggle compression force F T  to generate a moment M MS  defined by the equation M MS =F MS (A), where “A” is the distance between the line of direction of F MS  and the fulcrum point  101 . This moment M MS  is reacted to by the moveable contact  38  on the stationary contact  44  to generate a predetermined contact pressure force F C  and an equal and opposite contact pressure moment M C . The contact pressure moment M C  is defined by the equation M C =F C (B) where “B” is the distance between the line of direction of F C  and the fulcrum point  101 . The upper portion  62  of the auxiliary actuator  60  is positioned at the fulcrum point  101  and generates an auxiliary actuator force F AUX  which is substantially in line with the direction of the opposing toggle compression force F T . 
     It is important to maintain the predetermined contact pressure F C  between the moveable and stationary contacts  38  and  44  to insure proper circuit breaker  12  performance and to prevent premature wear on the contacts  38  and  44 . By positioning the actuator  60  at the fulcrum point  101 , the larger springs required to enable the auxiliary switch  14  to handle the higher interrupt current ratings of the circuit breaker  12  can be utilized without affecting the contact pressure F C  or the performance of the circuit breaker  12 . 
     Referring to FIG. 11, as is well known, the auxiliary switch contacts are discussed above as having a single pole, single throw, double break arrangement. However, it is also considered within the scope of this invention to have other contact arrangements as well. By way of example, a single pole, double throw, double break embodiment is shown in FIG.  12 . 
     Referring to FIG. 12, the contact lever  64  of the auxiliary switch  14  has an additional pair of moveable contacts  104  disposed on its opposing side. An additional pair of terminals  106  and  108  are connected to an additional pair of stationary contacts  110 . The terminals  30  and  32  could be connected in one circuit, and the terminals  106  and  108  could be connected to a separate circuit. Alternatively, terminals  30  and  106  or terminals  32  and  108  could be tied together in the same circuit. 
     Referring to FIG. 13, a wiring diagram of the auxiliary switch used as a neutral disconnect is shown. The line side of the source  112  is connected to terminal  26  which is in series with the circuit breaker contacts  38  and  44 , current sensing coil  48  and terminal  24  of the circuit breaker. The load line is connected in series to load  114 . The return side of the load is connected to auxiliary terminal  32  which is in series with auxiliary contacts  74  and  68 , and auxiliary terminal  30 . Auxiliary terminal  30  is in turn connected to the return side of the source  112  to complete the circuit. The full load current must conduct through both the circuit breaker contacts  38  and  44  on the line side of the circuit, and the auxiliary contacts  68  and  74  on the load side of the circuit. Since the auxiliary contacts  68  and  74  are mechanically tied to the circuit breaker contacts  38  and  44 , when the circuit breaker  12  disconnects the line side, the auxiliary switch  14  will disconnect the neutral side. 
     Referring to FIG. 14, a wiring diagram of the auxiliary switch  14  used in series with the circuit breaker  12  in a DC circuit is shown. In this embodiment the circuit breaker contacts  38  and  44  are in series connection with the auxiliary contacts  68  and  74  on the high side of a DC circuit between a DC source  116  and a load  118 . By connecting the auxiliary switch in this fashion, the DC interrupt capacity of the circuit breaker can be increased. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.