Abstract:
An operating handle assembly is provided having an improved handle engagement arrangement, thereby enabling the operating handle assembly to be adaptable for both human and machine interaction without the requirement of special attachment hardware. An operating handle assembly having a handle base and handle stem can accept a first handle extension suitable for human interaction or a second handle extension suitable for machine interaction. Assembly features provide for proper assembly of the handle extension to the handle stem while maintaining appropriate electrical clearances to live parts. The two part operating handle assembly, handle base with handle stem plus handle extension, provides for improved manufacturability of the host device, whereby the end-use construction of the host device need not be identified until a late point in the production cycle. The host device may be, but is not limited to, a standard circuit breaker, a rotary circuit breaker, a switch, or a disconnect device.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to an operating handle having a handle extension for use in a circuit breaker, such as a molded case circuit breaker, which has the function of connecting and disconnecting electrical power to and from a protected circuit that typically receives power through an electrical distribution panel. Handle extensions are well known in the art of circuit breakers. An example of a handle extension suitable for circuit breaker application is described in U.S. Pat. No. 5,075,659 entitled “Compact Molded Case Circuit Breaker Having External Contact Condition Indication” (&#39;659 patent), and U.S. Pat. No. 5,084,689 entitled “Compact Molded Case Circuit Breaker With Increased Ampere Rating” (&#39;689 patent).  
           [0002]    Operating handles with handle extensions that assist in the operation of a circuit breaker and provide indication of the handle position of a circuit breaker are not only employed in conventional single-contact-pair circuit breakers, but also in other devices, such as two-contact-pair rotary circuit breakers, switches, and disconnects. The applications that these devices are used in are vast, and include, but are not limited to, the utility, industrial, commercial, residential, and automotive industries. The primary function of an operating handle is to provide a means for mechanically interfacing with an operating mechanism to close and open electrical contacts, thereby connecting and disconnecting a protected circuit, respectively. An additional function of an operating handle is to provide a means for indicating the position of the electrical contacts, such as whether they are open or closed.  
           [0003]    The operating handle and handle extension must be suitable for both manual and automatic operation. If the circuit breaker, or other such device, is to be operated manually, the operating handle and handle extension must be suitable for human interaction. Alternatively, if the circuit breaker, or other such device, is to be operated automatically, the operating handle and handle extension must be suitable for machine interaction. Typically, an arrangement that is suitable for one type of interaction is not suitable for the other. For example, the aforementioned &#39;659 and &#39;689 patents describe a handle extension that is pivotally attached to an operating handle, whereby the handle extension provides a means for extending the length of the operating handle for improved manual operation of the circuit breaker. While removal of the handle extension would provide a shorter handle that could be used for automatically operating the circuit breaker, the presence of the resulting notch in the operating handle would result in a handle with reduced surface engagement for the interacting machine and undesirable wear to the interacting surfaces. Also, the pivotally attached handle extension requires special attaching hardware that has an appropriate fit for both safe operation and pivotal action. Thus, it would be beneficial to have an operating handle and handle extension that is suitable for both human and machine interaction and does not require special attachment hardware.  
         SUMMARY OF THE INVENTION  
         [0004]    In an exemplary embodiment of the present invention, an operating handle is provided having an improved handle engagement arrangement, thereby enabling the operating handle to be adaptable for both human and machine interaction without the requirement of special attachment hardware. An operating handle having a base stem can accept a first handle extension suitable for human interaction or a second handle extension suitable for machine interaction. Assembly features provide for proper assembly of the handle extension to the handle stem while maintaining appropriate electrical clearances to live parts. The two part operating handle, handle base with stem plus handle extension, provides for improved manufacturability of the host device, whereby the end-use construction of the host device need not be identified until a late point in the production cycle (i.e., late point identification). Such a host device may be, but is not limited to, a standard circuit breaker, a rotary circuit breaker, a molded case circuit breaker, a switch, or a disconnect device. Host devices such as circuit breakers are frequently employed in electrical distribution panels, which would also benefit from the advantages of the present invention.  
           [0005]    The operating handle assembly, including a handle base, base stem, and handle extension, can be made out of any material suitable for the application, including metal or plastic. While plastic may be more suitable for electrical applications because of the additional electrical isolation protection the plastic material provides, metal may also be suitable for electrical applications where the electrical isolation protection is provided by some other means. Suitable metals would include, but are not limited to, steel, stainless steel, brass, aluminum diecast, or zinc diecast. Thermoset-type plastics such as but not limited to polyester, polyester-glass, phenolic, phenolic-glass, epoxy, epoxy-glass, melamine, or melamine-glass, are well suited for operating handle applications because of their strength and electrical properties. Also suitable for operating handle applications are thermoplastic-type plastics such as but not limited to polyethylene, polypropylene, polystyrene, polyester, polyvinyl chloride, acrylics, nylons, spandex-type polyurethanes, polyamides, polycarbonates, fluorocarbons, and cellulosics, because of their flexural and electrical properties. An operating handle assembly manufactured from a thermoplastic-type plastic may be fabricated with snap-fit features to hold the assembly together, while an operating handle assembly manufactured from a thermoset-type plastic will typically require alternate fastening means, such as but not limited to a screw, bolt, pin or clip.  
           [0006]    The engagement of the handle extension to the handle stem must be sufficient to transmit the operational forces, exerted by either human or machine, from the handle extension to the handle stem without disengagement of the handle extension from the handle stem. Additionally, the engagement arrangement between handle extension and handle stem must be capable of transmitting the applied handle forces to the operating mechanism without over-stressing the engagement arrangement. The engagement arrangement between handle extension and handle stem can be achieved by a simple box-like arrangement with no ribs or slots. However, for improved transmission of forces between the handle extension and handle stem, ribs and slots are incorporated into the engagement arrangement, thereby providing auxiliary interacting surfaces. While there are many different shapes of ribs and slots that can be employed in an engagement arrangement, shapes that produce interacting surfaces that tend not to force apart the engagement arrangement are preferable. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 illustrates a perspective view of an electrical distribution panel incorporating the present invention;  
         [0008]    [0008]FIG. 2 illustrates an exploded perspective view of an electrical circuit breaker incorporating the present invention;  
         [0009]    [0009]FIG. 3 illustrates a cutaway side view of an electrical circuit breaker showing internal electrical components;  
         [0010]    [0010]FIG. 4 illustrates a partial perspective view of an arc chamber of an electrical circuit breaker;  
         [0011]    [0011]FIG. 5 illustrates a perspective view of an operating handle base incorporating the present invention;  
         [0012]    [0012]FIG. 6 illustrates a perspective view of a handle extension incorporating the present invention;  
         [0013]    [0013]FIG. 7 illustrates a perspective view of another handle extension incorporating the present invention;  
         [0014]    [0014]FIG. 8 is a view similar to FIG. 5 but of an alternative embodiment of this invention;  
         [0015]    [0015]FIG. 9 is a view similar to FIG. 6 but of an alternative embodiment of this invention;  
         [0016]    [0016]FIG. 10 is a view similar to FIG. 7 but of an alternative embodiment of this invention; and  
         [0017]    [0017]FIG. 11 illustrates an operating handle assembly with the handle extension in section view incorporating the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    Distribution Panel Generally  
         [0019]    An electrical distribution panel, well known to one skilled in the art of electrical distribution, is depicted generally in FIG. 1, is fully described in commonly assigned U.S. patent application Ser. No. 09/560,226 entitled “Electrical Distribution Panel With Split Neutral Bus” filed Apr. 28, 2000, functions generally to distribute protected power from a common main source to a plurality of branch circuits, and is described generally below.  
         [0020]    Referring to FIG. 1, an electrical distribution panel  200  includes a panel base  202 , a panel cover  204  and an interior assembly  206 . The panel base  202  and panel cover  204  generally make up the panel housing  208  of distribution panel  200 . The interior assembly  206  is attached to panel base  202  by suitable fasteners, not shown, through mounting holes  210 . Upstanding supports  212  are integral to interior assembly  206  and provide attachment surfaces  214  for attachment of panel cover  204 , which is secured to the attachment surfaces  214  by suitable fasteners, not shown, through holes  216  in panel cover  204 .  
         [0021]    Interior assembly  206  includes main support  218  for mechanically supporting a main circuit device, such as but not limited to a circuit breaker  10  that is fully described below, at least one busbar  220  for connecting circuit breaker  10  to a plurality of branch circuit connections  222 , a ground connector  224  for providing an electrical ground connection within the distribution panel  200 , and a neutral connector  226  for providing an electrical neutral connection within the distribution panel  200 . Power distribution to a plurality of branch circuits, not shown, is made through the plurality of branch circuit connections  222 .  
         [0022]    Circuit Breaker Generally  
         [0023]    A circuit breaker  10  incorporating the present invention is depicted in the exploded perspective view of FIG. 2. Cassette  12 , conventional trip unit  18   a  in trip unit housing  18   b  and conventional operating mechanism  16 , are captivated between cover  11  and case  17  by fasteners, not shown. Cassette halves  12   a,b  are secured by fasteners, not shown, and positionally located in pocket  22  of case  17 . For simplicity and clarity, where more than one element of the same type is present, only one will be referenced, but the reader will readily recognize that the single reference pertains to more than one element of the same type. Here, for example, there are three cassettes  12  and three pockets  22  where each cassette  12  is positionally located in an associated pocket  22 . Reference is made to a cassette  12  and a pocket  22  but the reader will readily recognize that three cassettes  12  and three pockets  22  are present. Also for simplicity and clarity, reference will only be made to a three phase circuit breaker, but the reader will recognize that the present invention is equally applicable to single phase, two phase or multi-phase electrical switching devices of any kind.  
         [0024]    Trip unit housing  18   b  is positionally located in pocket  23  of case  17 . Extending through opening  13  of escutcheon  14  on cover  11  is operating handle assembly  15 , which is operatively connected between operating mechanism  16  and movable contact arm  20  for opening and closing electrical contacts  21   a,b,c,d,  best seen by referring to FIG. 2.  
         [0025]    A conventional operating mechanism  16 , well known to one skilled in the art and depicted generally in FIG. 1, is fully described in commonly assigned U.S. patent application Ser. No. 09/196,706 entitled “Circuit Breaker Mechanism for a Rotary Contact System” filed Nov. 20, 1998, which is herein fully incorporated by reference. A conventional trip unit  18   a , depicted generally in FIG. 2 and in phantom in FIG. 3, is operatively connected between conventional current sensors  19 , depicted in phantom in FIG. 3, and operating mechanism  16  to effectuate the opening of contacts  21   a,b,c,d  upon the occurrence of an abnormal overcurrent condition. A conventional trip unit  18   a  and conventional current sensors  19  are well known to one skilled in the art and are fully described in commonly assigned U.S. Pat. Nos. 4,589,052, 4,728,914, and 4,833,563, which are herein fully incorporated by reference.  
         [0026]    Referring to FIG. 3, which depicts a cutaway side view of cassette  12  and trip unit housing  18   b  in case  17 , electrical connections between the protected circuit, not shown, and circuit breaker  10  are made through load terminal  30  on load side  31  of circuit breaker  10 . Electrical connections between the power source, not shown, and circuit breaker  10  are made through line terminal  32  on line side  33  of circuit breaker  10 .  
         [0027]    Referring to both FIGS. 2 and 3, circuit breaker  10  constructed in accordance with the present invention, includes operating handle assembly  15  for driving operating mechanism  16  to manually open and close electrical contacts  21   a,b,c,d.  Contact  21   a  is carried by elongated fixed contact arm  34 , contacts  21   b,c  are carried by elongated movable contact arm  20 , and contact  21   d  is carried by elongated fixed contact arm  35 . FIG. 3 also shows movable contact arm  20 ′, depicted in phantom, following an opening action by trip unit  18   a  and operating mechanism  16 . Fixed contact arm  34  extends through opening  36  of cassette  12  to terminate in line terminal  32 , which is accessible through an opening, not shown, in line side  33  of case  17 . Obviously, each phase of the multi-phase circuit breaker would have separate conductors per phase, not shown. Operating mechanism  16  is operatively connected to contact arm  20  by link  25 , rotor  26 , and connecting pins  27   a,b.    
         [0028]    The current path through circuit breaker  10  in the closed position is best seen by referring to FIG. 3. Under quiescent operating conditions, the current from the power source enters circuit breaker  10  through line terminal  32  (and other line terminals on adjacent phases not shown), and exits through load terminal  30  (and other load terminals on adjacent phases not shown). Between line terminal  32 , and load terminal  30 , the current path consists of; fixed contact arm  34 , electrical contacts  21   a  and  b,  movable contact arm  20 , electrical contacts  21   c  and  d,  fixed contact arm  35 , and sensor strap  39 . Sensor strap  39  passes through and provides primary current signal to current sensor  19 , which is operatively connected to trip unit  18   a . Fixed contact arm  35  is mechanically and electrically connected to sensor strap  39  by a fastener, not shown. Sensor strap  39  passes through openings, not shown, in trip unit housing  18   b  to terminate in load terminal  30 , which is accessible through an opening, not shown, in load side  31  of case  17 .  
         [0029]    Arc chute, or arc extinguishing, assembly  40  is removably captivated within cassette  12  by molded detail  43  that is integral to cassette  12 , and is best seen by referring to FIGS. 3 and 4. Arc plates  41 , are typically, but not necessarily, arranged substantially parallel to one another, have tabs  44  that are captivated in corresponding slots in plate supports  42 . Exhaust baffle  50  is removably captivated within cassette  12  by molded slot  45 , shown in phantom in FIG. 3, that is integral to cassette  12 . An X-slot  51  and rectangular slots  52  are formed in exhaust baffle  50 , thereby providing through holes in exhaust baffle  50  for the passage of arc effluent generated from a short circuit interruption condition. The arc effluent passing through exhaust baffle  50  on line side  33  of circuit breaker  10  will exit case  17  through terminal chamber  37 . The arc effluent passing through exhaust baffle  50  on load side  31  of circuit breaker  10  will exit case  17  through vent channel  38 , shown in phantom in FIG. 2. Vent channels  38  are fully described in commonly assigned U.S. patent application Ser. No. 09/366,473 entitled “Bottom Vented Circuit Breaker Capable of Top Down Assembly Onto Equipment” filed Aug. 3, 1999, which is herein fully incorporated by reference.  
         [0030]    Circuit Breaker Operating Handle Assembly  
         [0031]    Referring now to FIGS. 5, 6 and  7 , operating handle assembly  15 , shown in FIG. 2, consists of handle base  60  and one of either handle extension  80  or handle extension  80 ′ coupled thereto. Handle base  60  includes handle stem  62 , offset shelf  64 , first recess  66 , second recess  68 , and coupling pilot hole  70 . Handle extension  80  and  80 ′ includes operator interface surface  82 ,  82 ′, extension pocket  84 ,  84 ′, first projection  86 ,  86 ′, second projection  88 ,  88 ′, coupling through-hole  90 ,  90 ′, and engagement surface  92 ,  92 ′.  
         [0032]    Handle extension  80  is assembled onto handle base  60  by aligning first and second projections,  86 ,  88 , with first and second recesses  66 ,  68 , respectively, and sliding extension pocket  84  over handle stem  62  until engagement surface  92  abuts offset shelf  64 . A coupling screw, not shown, is inserted through coupling through-hole  90  and into coupling pilot hole  70 . Coupling through-hole  90  is sized to permit passage of the threads of coupling screw, while coupling pilot hole  70  is sized to create an interference fit with the threads of coupling screw, thereby permitting the use of a coupling screw with self-tapping threads to securely engage handle extension  80  with handle base  60 .  
         [0033]    As can be seen by comparing like elements of handle extension  80  shown in FIG. 6 with handle extension  80 ′ shown in FIG. 7, a description of the assembly process of one will also apply to the other.  
         [0034]    First and second recesses  66 ,  68 , and first and second projections  86 ,  88 , are offset from one another in the “Y” direction and by the same amount, thus requiring handle extension  80  to be oriented with first projection  86  aligned with first recess  66 , and second projection  88  aligned with second recess  68  for proper assembly of handle extension  80  onto handle stem  62 , thereby providing interference detail, or alternatively a rejection means, to prevent misalignment of handle extension  80  with handle stem  62 . Additionally, coupling pilot hole  70  and coupling through-hole  90  are located off of the central “Z” axis of handle stem  62 , thus providing additional asymmetry for proper assembly of handle extension  80  to handle stem  62 , and providing appropriate electrical clearance from the coupling screw to the underside of handle base  60  where mechanism parts are in the proximity of the central “Z” axis. Some handle assembly designs may not require a rejection means by the offsetting of the engagement projections, recesses and coupling means, and therefore both symmetrical and asymmetrical handle extension arrangements are contemplated by the present invention.  
         [0035]    The profiles of the cross-sectional areas of projections  86 ,  86 ′,  88 ,  88 ′, and recesses  66 ,  68 , taken with respect to a “Z” plane (a “Z” plane is a plane perpendicular to the “Z” axis) (also, a “Z” plane is represented by surfaces  72 ,  94  and  94 ′), are shown in FIGS. 5, 6, and  7 , to be rectangular. While the engagement of a rectangular projection, such as but not limited to a rib, with a rectangular recess, such as but not limited to a slot, will provide interacting surfaces  74   a,b,c,d  (side walls), and  96   a,b,c,d  (side edges), with action-reaction force vectors in the direction of the “Y” axis, such an arrangement is not intended to be limiting. Other profiles that could be employed for the cross-sectional areas of the projections and recesses include, for example, a circle, triangle or dove tail. While each of these alternative profiles would produce an “X”-direction force component between interacting surfaces  74 ,  96 ,  96 ′, which ordinarily would be undesirable because of the increased handle stress or cam-out action, they may be appropriate for low force-generating handle designs.  
         [0036]    The completed handle assembly  15  results in handle extension  80  being securely coupled to handle base  60  by means of coupling screw, or other suitable fastener, not shown, and engagement surface  92  abutting offset shelf  64 . In the assembled state, handle extension  80  cannot move relative to handle base  60 . In essence, the two have become one and move in unison. The advantage of a two-part assembly as opposed to a one-piece part is seen by considering the manufacturing process, where the end product may be configured for a customer requesting a manually operated device or for a customer requesting a machine operated device. Removal and replacement of handle extension  80  from handle base  60  can be easily accomplished by removal and replacement of the coupling screw.  
         [0037]    With a manually operated device, handle extension  80 ′ having contoured surface  98 ′ would be employed. Here, contoured surface  98 ′ is purposefully designed with human interaction in mind where length “L” of handle extension  80 ′ is designed to provide appropriate leverage for operating circuit breaker  10 . Contoured surface  98 ′ provides for ease of operation of the switching device when operated by human hand, not shown, and a customer with large clearance around the handle assembly  15  could choose a handle extension  80 ′ with a large “L” dimension, while a customer with limited clearance around the handle assembly  15  would choose a handle extension  80 ′ with a small “L” dimension.  
         [0038]    With a machine operated device, handle extension  80  having planar surface  98  would be employed. Here, planar surface  98  is purposefully designed with machine interaction in mind where length “I” of handle extension  80  is designed to work effectively with the output force of interacting machinery, not shown. Planar surface  98  provides for uniform surface stress distribution since it is void of stress-concentrating detail, such as projections or recesses, and length “I” could be chosen to work effectively with the output characteristics of a customer&#39;s operating equipment, not shown. Length “L” of handle extension  80 ′ is typically, but not necessarily, greater than length “I” of handle extension  80  since ease of operation of the switching device is generally more relevant when human interaction, as opposed to machine interaction, is involved.  
         [0039]    Alternative Embodiment of Circuit Breaker Operating Handle Assembly  
         [0040]    Handle extension  80  to handle base  60  coupling means has been described above as involving a coupling screw, not shown, inserted through coupling through-hole  90  and into coupling pilot hole  70 . Coupling through-hole  90  is sized to permit passage of the threads of coupling screw, while coupling pilot hole  70  is sized to create an interference fit with the threads of coupling screw, thereby permitting the use of a coupling screw with self-tapping threads to securely engage handle extension  80  with handle base  60 . While many types of coupling screws can be employed, such as round head, pan head, or flat head, countersink  91  indicates that the present invention employs a flat head coupling screw. An alternative coupling means to the coupling screw, which would eliminate the countersink  91  detail, is a snap fit coupling means, which is best seen by now referring to FIGS. 8, 9 and  10 . For simplicity and clarity, elements shown in FIGS. 8, 9 and  10  that are identical to like elements in FIGS. 5, 6 and  7 , are not enumerated but perform identical functions.  
         [0041]    Engagement catch detail  102  on handle base  100 , shown in FIG. 8, includes first relief  104 , engagement catch surface  106 , angled catch surface  107 , and second relief  108 . Flexible engagement latch  122  on handle extension  120 , shown in FIG. 9, includes extension leg  124 , engagement latch surface  126 , and angled latch surface  127 . Handle extension  120  is assembled onto handle base  100  by aligning flexible engagement latch  122  on handle extension  120  with engagement catch detail  102  on handle base  100 , and by aligning first and second projections,  86 ,  88  on handle extension  120  with first and second recesses  66 ,  68  on handle base  100 , respectively, and then sliding extension pocket  84  on handle extension  120  over handle stem  62  on handle base  100  until engagement surface  92  on handle extension  120  abuts offset shelf  64  on handle base  100 . During the assembly process, angled latch surface  127  on flexible engagement latch  122  engages angled catch surface  107  on engagement catch detail  102  causing extension leg  124  to flex outward, thereby permitting engagement latch surface  126  to relax into second relief  108  and engage with engagement catch surface  106  prior to engagement surface  92  abutting offset shelf  64 .  
         [0042]    As can be seen by comparing like elements of handle extension  120  shown in FIG. 9 with handle extension  120 ′ shown in FIG. 10, a description of the assembly process of one will also apply to the other. Operation of Handle Assembly Generally Under quiescent operating conditions with the electrical switching device turned ON, operating mechanism  16  and electrical contacts  21   a,b,c,d  are in a closed condition. Since operating mechanism  16  is operatively connected to contact arm  20  by link  25 , rotor  26 , and connecting pins  27   a,b,  the electrical switching device can be turned OFF by actuating operating handle assembly  15  to position operating mechanism  16  and electrical contacts  21   a,b,c,d  in an open condition. The actuation of operating handle assembly  15  requires an external force, from either a human or machine source, to be applied to handle extension  80 . Generally, but not necessarily, an external force originating from a machine source is applied to handle extension  80  or  120 , while an external force originating from a human source is applied to handle extension  80 ′ or  120 ′. Hereinafter reference will be made to handle extension  80 , but the discussion will equally apply to handle extension  80 ′,  120 , and  120 ′, unless otherwise indicated.  
         [0043]    Reference is now made to FIG. 11, which has some detail missing for clarity. When an external force “F” from an external environment, that is, an environment outside of the circuit breaker, is applied to handle extension  80 , handle extension  80  is biased in the direction of the applied force, resulting in contact between internal wall  85  of extension pocket  84  and associated external wall  63  of handle stem  62 , and resulting in contact between side edges  96  of projections  86 ,  88  and associated side walls  74  of recesses  66 ,  68 . The biasing of handle extension  80  against handle stem  62  is further represented by the presence of gaps  130   a,b  between handle extension  80  and handle stem  62 . The interaction of these multiple surfaces effectively transmits the applied external force “F” from handle extension  80  to handle base  60 , thereby providing the means to actuate operating mechanism  16 , which is operatively connected to handle base  60 , from ON to OFF and from OFF to ON.  
         [0044]    While this 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. In addition, many modifications may be made 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.  
                                             Element List                                     10   circuit breaker            11   cover            12   cassette            12a,b   cassette halves            13   opening            14   escutcheon            15   operating handle assembly            16   operating mechanism            17   case            18a   trip unit            18b   trip unit housing            19   current sensors            20   movable contact arm            20′   movable contact arm - phantom            21a-d   electrical contacts            22   pocket            23   pocket            25   link            26   rotor            27a,b   connecting pins            30   load terminal            31   load side            32   line terminal            33   line side            34   fixed contact arm            35   fixed contact arm            36   opening            37   terminal chamber            38   vent channel            39   sensor strap            40   arc chute            43   molded detail            41   arc plates            42   plate supports            44   tabs            45   molded slot            50   exhaust baffle            51   x-slot            52   rectangular slots            60   handle base            62   handle stem            63   external wall            64   offset shelf            66   first recess            68   second recess            70   coupling pilot hole            72   surface            74a-d   interacting surfaces (side walls)            80   handle extension            80′   handle extension            82   operator interface surface            82′   operator interface surface            84   extension pocket            84′   extension pocket            85   internal wall            86   first projection            86′   first projection            88   second projection            88′   second projection            90   coupling through-hole            90′   coupling through-hole            91   countersink            92   engagement surface            92′   engagement surface            94   surface            94′   surface            96a-d   interacting surfaces (side edges)            96′a-d   interacting surfaces (side edges)            98   planar surface            98′   contoured surface           100   handle base           102   engagement catch detail           104   first relief           106   engagement catch surface           107   angled catch surface           108   second relief           120   handle extension           120′   handle extension           122   engagement latch detail           124   extension leg           126   engagement latch surface           127   angled latch surface           130a,b   gaps           200   distribution panel           202   panel base           204   panel cover           206   interior assembly           208   panel housing           210   mounting holes           212   upstanding supports           214   attachment surfaces           216   holes           218   main support           220   at least one busbar           222   plurality of branch circuit connections           224   ground connector           226   neutral connector