Abstract:
A disconnect is coupled to a rotary shaft communicating with a door-mounted knob provides an operator on the shaft for engaging the door handle to detect closure of the door. The operator includes a pair of coupling mechanisms that control the transmission of torque between the operator and the shaft depending on whether the door is open or closed. Specifically, when the door is open, torque applied to the operator in both directions is transmitted to the shaft. If the door is open, torque applied to the operator is only transmitted in one direction to disconnect power through the disconnect unless the user performs a predetermined sequence of events to rotatably couple the operator to the shaft with respect to rotation in the opposite direction that connects power through the disconnect.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Continuation-In-Part of U.S. patent application S/N 10/714,433 filed Nov. 14, 2003, which is in turn a Continuation-in-Part of U.S. patent application S/N 10/298,326, filed Nov. 18, 2002, the disclosure of each of which is hereby incorporated by reference as if set forth in its entirety herein. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates to electrical disconnects for mounting in cabinets and having a forwardly-extending, rotary shaft that may engage a handle on the cabinet door when the cabinet door is closed, and in particular to an improvement in such a disconnect that reduces the chance of current flowing through the disconnect when the cabinet door is open.  
         [0004]     Referring to  FIG. 1 , a disconnect in the form of a standard fuse block  10  of the prior art may receive fuse cartridges  12  along its front face and may attach at its rear face to the rear wall  14  of a metal cabinet  16 .  
         [0005]     Input terminals along the top of fuse block  10  may receive wires  18  which connect independently to one side of each fuse cartridge  12 , the latter which interconnect wires  18  to wires  20  attached to output terminals along the bottom of the fuse cartridge  12 . Wires  18 , for example, may be connected to a source of three-phase power and wires  20 , for example, may be connected to a motor or other piece of equipment.  
         [0006]     Fuse block  10  may be activated to electrically disconnect wires  18  from the respective fuse cartridges  12 . The fuse block  10  may be controlled by a rotary shaft  22  along one side of the fuse block  10  and extending in an orientation perpendicular to the rear wall  14  of cabinet  16  toward an open face of the cabinet.  
         [0007]     The open face of the cabinet may be covered by a door  24  attached by hinges to one side of the cabinet  16 . Door  24  may support a captively mounted rotary knob  26  having an inwardly extending connector  28 .  
         [0008]     Referring now to  FIG. 2 , knob  26  may include connector  28  that extends inwardly through an opening in the door  24 . Connector  28  includes retaining flanges  30  for retaining it rotatably within that opening.  
         [0009]     When door  24  is closed about the cabinet  16 , connector  28  of the knob  26  engages the outermost end of rotary shaft  22 , thereby allowing rotary shaft  22  to be operated by knob  26  when door  24  is closed on cabinet  16 . Specifically, an inwardly facing end of connector  28  may include a keyway  32  receiving a rectangular end of rotary shaft  22  and a pin  34  extending perpendicularly through the rotary operator. Turning knob  26 , in turn, rotates shaft  22  to electrically disconnect or connect power to wires  20 .  
         [0010]     Referring again to  FIG. 1 , knob  26  allows disconnection of power to wires  20  when the door  24  on the cabinet  16  is closed. However, when door  24  is open, rotary shaft  22  is exposed, thereby enabling power to be inadvertently reconnected by counter rotation the shaft  22 .  
         [0011]     One apparatus for preventing the reconnection of power while the door is open includes bracketing that is connected to the exterior of fuse block  10 . The bracketing enables knob rotation to connect and disconnect the power when the door is closed, and further prevents inadvertent counter rotation of the knob to reconnect the power when the door is open. While this apparatus is suitable for its intended purpose, the bracketing requires modification of an existing fuse block.  
         [0012]     It would therefore be desirable to provide a less intrusive mechanism for preventing rotation of the operator in a direction that would reconnected power when the cabinet door is open.  
       BRIEF SUMMARY OF THE INVENTION  
       [0013]     One aspect of the present invention provides an operator assembly for controlling a disconnect having a rotary shaft adapted to receive a portion of a door-mounted knob and rotating in a first direction to connect electrical current through the disconnect, and rotating in a second direction to prevent electrical current from flowing through the disconnect. The operator assembly includes a housing configured to receive the rotary shaft, and a unidirectional coupling mechanism that is connected between the shaft and the housing, wherein the uni-directional coupling mechanism facilitates uni-directional rotation of the shaft in response to rotation of the operator assembly.  
         [0014]     It is thus one object of the invention to prevent power from being connected and disconnected simply by rotating the operator housing.  
         [0015]     In another aspect, the operator assembly includes a bi-directional coupling mechanism that couples the shaft and the handle with respect to both directions of handle rotation when the door is closed.  
         [0016]     It is thus another object of the invention to enable current to be intuitively connected through the disconnect and to prevent current from flowing through the disconnect when the door is closed by rotating the handle in the corresponding direction.  
         [0017]     In accordance with yet another aspect of the invention, the bi-directional coupling mechanism can be engaged by the user when the door is open by performing a predetermined sequence of events.  
         [0018]     It is thus another object to enable a skilled user to intentionally connect power to the disconnect when the door is open while reducing the likelihood that power will be inadvertently connected.  
         [0019]     In still another aspect, the operator assembly includes a clutch that engages the bi-directional coupling mechanism when either the door is closed or the user performs the predetermined sequence of events.  
         [0020]     It is thus another object of the invention to provide a mechanism for activating the bi-directional coupling mechanism, and operating the uni-directional coupling mechanism when the bi-directional coupling mechanism is disengaged.  
         [0021]     In another aspect, the clutch is operated by depressing a hub relative to the handle to engage the bi-directional coupling mechanism and releasing the hub relative to the handle to disengage the bi-directional coupling mechanism and engage the secondary coupling mechanism.  
         [0022]     It is thus another object to engage the bi-directional coupling mechanism automatically when the door is closed, to selectively engage the bi-directional coupling mechanism when the door is open, and to automatically engage the uni-directional coupling mechanism when the bi-directional coupling mechanism is disengaged.  
         [0023]     In another aspect, the operator assembly is carried by the shaft.  
         [0024]     It is thus another object to provide an operator assembly that can be retrofitted to a pre-existing disconnect without requiring modification of the disconnect.  
         [0025]     These and other aspects and advantages of the present invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part thereof, and in which there is shown by way of illustration, and not limitation, preferred embodiments of the invention. Such embodiments do not necessarily represent the full scope of the invention, and reference should therefore be made to the claims herein for interpreting the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a perspective view of a prior art fuse block described above and mounted to the rear of a cabinet and having a forwardly extending rotary disconnect operator that may be received by a door-mounted handle when the cabinet door is closed;  
         [0027]      FIG. 2  is a fragmentary view of the door-mounted handle immediately before engagement with the rotary disconnect operator as known in the prior art;  
         [0028]      FIG. 3  is a perspective view of a fuse block mounted to the rear of a cabinet and having a forwardly extending rotary disconnect shaft extending through an operator assembly having a handle constructed in accordance with the preferred embodiment;  
         [0029]      FIG. 4  is a perspective view of the operator assembly illustrated in  FIG. 3  that receives the shaft;  
         [0030]      FIG. 5  is an assembly view of the operator assembly illustrated in  FIG. 3   
         [0031]      FIG. 6  is a side elevation view of the operator assembly illustrated in  FIG. 3  when the door is open;  
         [0032]      FIG. 7  is a side elevation view of the operator assembly illustrated in  FIG. 3  when the door is closed;  
         [0033]      FIG. 8  is a sectional side elevation view of the operator assembly in the position illustrated in  FIG. 6 ;  
         [0034]      FIG. 9  is a sectional side elevation view of the operator assembly in the position illustrated in  FIG. 7 ;  
         [0035]      FIG. 10  is a top plan view of the operator assembly illustrated in  FIG. 3 ;  
         [0036]      FIG. 11  is a bottom view of the operator assembly illustrated in  FIG. 3 ;  
         [0037]      FIG. 12  is an assembly view of the operator assembly illustrating a bi-directional coupling mechanism;  
         [0038]      FIG. 13  is a partial sectional elevation view of the operator assembly showing the bi-directional coupling mechanism taken along line  13 - 13  of  FIG. 9 ;  
         [0039]      FIG. 14  is an assembly view of a uni-directional coupling mechanism;  
         [0040]      FIG. 15  is a sectional top elevation view of the uni-directional coupling mechanism illustrated in  FIG. 14 ;  
         [0041]      FIG. 16  is a sectional top elevation view of the uni-directional coupling mechanism similar to  FIG. 15  as the operator assembly is rotated clockwise;  
         [0042]      FIG. 17  is a top plan view of a uni-directional coupling mechanism constructed in accordance with an alternative embodiment;  
         [0043]      FIG. 18  is a top plan view of a uni-directional coupling mechanism constructed in accordance with another alternative embodiment;  
         [0044]      FIG. 19  is a top plan view of a uni-directional coupling mechanism constructed in accordance with still another alternative embodiment; and  
         [0045]      FIG. 20  is a top plan view of a uni-directional coupling mechanism constructed in accordance with yet another alternative embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0046]     Referring to  FIGS. 3 and 4 , the present invention modifies the fuse block  10  described above by mounting an operator assembly  36  to the axially outer end of a rotary shaft  22  coupled to the fuse block  10 . While an exemplary embodiment of the present invention is described as controlling electrical current through fuse block, it should be appreciated that the present invention is applicable to any electrical disconnect, including fuses, circuit breakers, and traditional switches.  
         [0047]     Operator assembly  36  extends generally axially, and interfaces with door knob  26  and, in particular, with connector  28 . Operator assembly  36  is thus operable by a user to connect power to fuses on fuse block  10 , and disconnect power from fuse block  10 . Operator assembly  36  preferably comprises a plastic, though one skilled in the art will recognize that any material suitable to withstand the stress and strain experienced during operation falls within the scope of the present invention.  
         [0048]     Referring now to  FIG. 5  in particular, one exemplary embodiment of operator assembly  36  is formed from a housing including an inner shell  38  fastened to an outer handle that retains a uni-directional coupling mechanism  64 , a clutch  43  including a spring  39 , and an inner cylindrical hub  44 . Operator assembly  36  is carried by the axially outer end of shaft  22 .  
         [0049]     Referring also to  FIG. 11 , inner shell  38  includes an annular cup  56  open at its axially outer end and closed at its axially inner end by an end face  58 . A circular aperture  55  extends axially through face  58 , and is centrally disposed to pass shaft  22 . The diameter of aperture  55  is greater than the largest cross-sectional dimension across shaft  22  such that rotation of shell  38  does not cause face  58  to impart rotational forces onto shaft  22 . A clip  96  is provided that includes a pin  98  and a fastener clamp  100 . Pin  98  is inserted through an aperture  101  extending radially through shaft  22 , and is retained by clamp  100  which applies radial pressure against shaft  22 . Clip  96  abuts face  58  and, accordingly, the axial location of aperture  101  determines the position of operator assembly  36  with respect to shaft  22 .  
         [0050]     A plurality of beveled ribs  60  extends axially along the radially inner surface of body  56 . Ribs  60  are equally spaced circumferentially about body  56  to define a plurality of interposed recesses  62 . A plurality of radially spaced teeth  59  extends axially out from the outer end of body  56 , and are equally spaced circumferentially about body  56  to define a corresponding plurality of interposed recesses  61 . A pair of opposing mounting flanges  57  extends radially out from the axially outer end of body  56 , and includes a pair of apertures sized to receive corresponding screws  54 .  
         [0051]     Referring now to  FIGS. 5 and 14 - 16 , a uni-directional coupling mechanism  64  is provided in the form of a ratchet assembly that enables uni-directional operation to disconnect power from fuse block  10 . Ratchet assembly  64  includes a bearing cup  66  having a hexagonal outer wall  68  that is sized to be received by ribs  60  such that rotation of inner shell causes cup  66  to correspondingly rotate. Cup  66  further includes an internal substantially cylindrical bore  70  forming a grooved ratchet chamber. Specifically, a track  73  defined by a plurality of axially extending arc-shaped grooves  71  (and corresponding teeth  75  interposed between adjacent grooves  71 ) defines the outer periphery of chamber  70 .  
         [0052]     Chamber  70  is closed at its axially inner end by a base  72  having a circular opening  74  extending centrally there through that is sized to loosely and rotatably pass shaft  22 . A hexagonal cover  77  is provided and affixed to the axially outer end of bearing cup  66 . Cover  77  is preferably transparent, and defines a central aperture  79  that matches aperture  74 . As a result, rotation of shaft  22  does not directly cause bearing cup  66  and cover  77  to rotate.  
         [0053]     Ratchet assembly  64  further includes a bearing carrier plate  76  having a generally cylindrical outer wall  78  having a diameter slightly less than the inner diameter of chamber  70 . An aperture  85  extends axially through carrier plate  76 , and defines a square or other suitable cross-section configured to snugly receive shaft  22  such that rotation of shaft  22  causes carrier plate  76  to rotate therewith. Specifically, outer wall  78  rides along grooves  71  as carrier plate  76  rotates within chamber  70  during operation.  
         [0054]     A pair of opposing elongated rectangular cutouts forms pockets  78  in carrier plate  76  offset 180° with respect to each other. Each pocket  78  is defined by first guide wall  80  and a second support wall  82  oriented perpendicular to guide wall  80 . Guide wall  80  is elongated with respect to support wall  82 . Each pocket  78  receives a spherical bearing member  84  supported by one end of a compression spring  86  that is grounded at its other end by support wall  82 . Each spring  86  biases its corresponding bearing member  84  against grooved track  73 .  
         [0055]     When a counterclockwise torque is applied to bearing cup  66 , the force causes teeth  75  to bias bearing members  84  against the corresponding non-resilient guide walls  80 . The counterclockwise torque is thus transferred to carrier plate  76 . Accordingly, bearing cup  66 , carrier plate, and shaft  22  all rotate counterclockwise.  
         [0056]     On the contrary, when a clockwise torque is applied to bearing cup  66  as indicated by Arrow A, bearing cup  66  is caused to rotate clockwise. As bearing cup  66  rotates, the radial forces resulting from engagement between bearing members  84  and teeth  75  cause springs  86  to compress. The compression causes bearing members  84  to slide along guide wall  80  as they cam over teeth  75  and fall into adjacent grooves  71  whose surfaces are defined by a radius that generally match the radius of bearing members  84 . Bearing members  84  continue to ratchet along track  73  as carrier plate  76  continues to rotate clockwise.  
         [0057]     Referring now to  FIGS. 17-19 , ratchet assembly  64  is illustrated in accordance with several alternative embodiments having any number of pockets  78  formed in carrier plate  76 . Specifically, as illustrated in  FIG. 17 , three pockets  78  can be oriented 120° with respect to each other in carrier plate  76 . Because an additional pocket  78  is provided and an additional bearing member  84  engages track  73 , additional torque is required to cause each bearing member  84  to slide along track  73  as bearing cup  66  is rotated counterclockwise. The required amount of driving torque can be increased still by providing four pockets  78  oriented 90° with respect to each other as illustrated in  FIG. 18 . Alternatively, the required amount of driving torque can be decreased by providing a single pocket  78  as illustrated in  FIG. 19 .  FIG. 19  further illustrates bearing cup outer wall  68  as being square-shaped and sized to engage ribs  60  in accordance with one of several alternative configurations of outer wall  68  intended to fall within the scope of the present invention.  
         [0058]     Referring to  FIG. 20 , bearing cup  66  can be provided with a track  73  having a smooth surface as an alternative to grooves  71 . Because the frictional resistance imparted onto bearing member  84  by smooth track  73  is reduced, the torque necessary to rotate bearing member  83  along track  73  is also reduced with respect to the grooved track described above. Furthermore, because a line extending tangentially to smooth track  73  at a location adjacent bearing member  84  intersects a line extending along guide wall  80 , bearing member  84  will engage track  73  when a counterclockwise torque is applied to bearing cup  66 , thereby rotatably coupling bearing cup  66  and carrier plate  76 .  
         [0059]     Referring now to  FIGS. 5 and 8 , hub  44  includes a generally cylindrical body  50  defining an internal seat that receives one end of a coil spring  39  that is seated at its opposite end against the outer axial surface of cover  77 . Spring  39  is a compression spring that provides a force biasing hub  44  axially out towards handle  40 .  
         [0060]     Cylindrical body  50  is closed at one end by an axially front face  46  sized to be engaged by connector  28 . Accordingly, when door  24  is closed, connector  28  depresses hub  44  against the force of spring  39 .  
         [0061]     An aperture  65  extends axially through hub  44 , and defines a square cross-section configured to snugly receive shaft  22  such that rotation of hub  44  causes shaft  22  to also rotate. It should be easily appreciated, however, that shaft  22  and aperture  65  (along with the other shaft-engaging components) could assume any alternative cross-sectional shape without departing from the present invention. The axially outer end of aperture  65  defines a keyway  47  extending only partially into hub  44  sized to receive a pin  34  extending transverse from the axially outer end of shaft  22 . Shaft  22  and hub  44  thus rotate in concert while keyway  47  prevents shaft  22  from being pulled through hub  44 .  
         [0062]     Referring also to  FIGS. 12 and 13 , a bi-directional coupling mechanism  67  includes a plurality of beveled pawls  52  extending radially out from the axially inner end of body  50  and are equally spaced circumferentially about body  50  to define interposed recesses  53  that are sized to receive ribs  60 . Likewise, pawls  52  are received by recesses  62 . It will thus be appreciated that the diameter defined by opposing recesses  62  is slightly greater than the diameter defined by opposing pawls  52 , and the diameter defined by opposing ribs  60  is slightly greater than the diameter defined by opposing recesses  53  but less than the diameter formed by opposing pawls  52 . Coupling mechanism  67  is engaged and disengaged by clutch  43  as hub  44  is depressed and released, respectively, relative to shell  38 , as is described in more detail below.  
         [0063]     When bi-directional coupling mechanism  67  is engaged, pawls  52  and ribs  60  interlock hub  44  and shell  38  with respect to rotation. Accordingly, rotation of operator assembly  36 , and in particular shell  38 , in both the clockwise and counterclockwise directions causes hub  44  and shaft  22  to correspondingly rotate.  
         [0064]     Referring again to  FIG. 5 , handle  40  is defined by an axially extending annular neck  48  that is connected at its outer end to a fluted grip  42  extending radially out from the axially outer end of handle  40 . Grip is thus configured to be intuitively engaged by the hand of a user to rotate operator assembly  36  in the clockwise and counterclockwise directions, selectively causing an internal fuse block switch (not shown) to connect and disconnect, respectively, power in fuse block  10 . It should be appreciated, however, that these directions of rotation can be reversed as desired to connect and disconnect the power.  
         [0065]     A plurality of radially spaced notches  49  are formed in the axially inner end of neck  48 , and are equally spaced circumferentially about neck  48 , to define a corresponding plurality of locking teeth  51  interposed between adjacent notches  49 . Teeth  59  and recesses  61  of shell  38  are configured to interlock with teeth  49  and recesses  51 , respectively, of handle  40 . A pair of threaded apertures  45  extends axially into grip  42  and face corresponding mounting flanges  57 . Screws  54  thus extend through flanges  57  and into apertures  45  to secure handle  40  to shell  38 .  
         [0066]     Referring also to  FIG. 10 , annular neck  48  defines an inner diameter sized to receive cylindrical hub  44 . An annular flange  35  extends radially in from neck  48  that is sized sufficiently large to receive cylindrical body  50  of hub  44 , but is sufficiently small to abut the axially outer edges of pawls  52 . Flange  35  thus provides a stop that prevents hub  44  from sliding through handle  40  during operation while enabling relative rotation between handle  40  and hub  44  (i.e., when bi-directional coupling mechanism  67  is disengaged).  
         [0067]     System Operation  
         [0068]     Operation of operator assembly  36  will now be described with initial reference to  FIGS. 6 and 8  illustrating door  24  in an open position and hub  44  in its normal position biased outwards by spring  39 . In this position, pawls  52  are axially displaced and disengaged from ribs  60 , thus illustrating bi-directional coupling mechanism  67  in a disengaged position. As a result, when a user rotates operator assembly  36  (e.g., via handle  40 ), the disengaged coupling mechanism  67  does not cause shaft  22  to correspondingly rotate.  
         [0069]     Rather, referring to  FIGS. 15 and 16 , uni-directional coupling mechanism  64  operates as described above. Specifically, when a user applies a torque to operator assembly  36  in the counterclockwise direction, for example via handle  40  (i.e., in an attempt to disconnect power in fuse block  10 ), inner shell ribs  60  impart a corresponding counterclockwise force onto bearing cup  66  which, in turn, causing bearing members  84  to engage grooved track  73  and rotatably couple bearing cup  66  and carrier plate  76 . Accordingly, counterclockwise rotation of operator assembly  36  causes carrier plate  76  (and shaft  22 ) to correspondingly rotate, thus allowing power to be disconnected in fuse block  10 .  
         [0070]     On the contrary, when a torque is applied to operator assembly  36  in the clockwise direction (i.e., in an attempt to connect power in fuse block  10 ), bearing member(s)  84  compress corresponding spring(s)  86  and ratchet along track  73 . Accordingly, bearing cup  66  rotates about carrier plate  76  (and shaft  22 ), thus preventing power from being reconnected in fuse block  10 . Furthermore, because operator assembly  36  is allowed to freely rotate in the clockwise direction, uni-directional coupling mechanism  64  provides tactile feedback that power is not permitted to be connected to fuse block  10  by simply rotating operator assembly  36 . Moreover, if the user is attempting to disconnect power from fuse block  10 , coupling mechanism  64  induces the user to rotate operator assembly  36  in the opposite, and correct, direction.  
         [0071]     The present inventors have recognized that certain internal disconnect switches in fuse block  10  are configured to operate under a low amount of torque. The amount of torque necessary to cause bearing members  84  to ratchet along track  73  can be controlled at each individual pocket  78 , for example, by adjusting the spring constant of spring  86 , the geometric configuration of teeth  75 , and the size of bearing members  84 . Alternatively, the driving torque force can be controlled by the number of pockets  78  formed in carrier plate  76  as described above. Advantageously, the amount of torque necessary to cause bearing members  84  to ratchet along track  73  is less than the amount of torque necessary to operate the disconnect switch.  
         [0072]     Referring now to  FIGS. 7, 9 , and  12 , bi-directional coupling mechanism  67  can be engaged in one of two ways. First, door  24  can be closed, thus causing connector  28  to depress hub  44  relative to inner shell  38  against the biasing forces of spring  39  as indicated by Arrow B. Secondly, bi-directional coupling mechanism  67  can be engaged by manually depressing hub  44  relative to operator assembly  36  by either depressing hub  44  directly, or by pulling handle  40  out, thus raising inner shell  38  relative to hub  44 . Whether door  24  is closed or hub  44  is manually depressed relative to shell  38 , pawls  52  become interdigitated with ribs  60  thus rotatably interlocking hub  44  and operator assembly  36 . The beveled ends of pawls  51  and ribs  60  assist in engaging coupling mechanism  67 . Because shaft  22  is coupled to hub  44 , when operator assembly  36  is rotated clockwise and counterclockwise with bi-directional coupling mechanism  67  engaged, shaft  22  rotates along with operator assembly  36  causing power to be connected and disconnected, respectively.  
         [0073]     It is thus appreciated that when door  24  is closed and a user wishes to access fuse block  10 , the user actuates knob  26 , which causes operator assembly  36  to rotate counterclockwise, thereby disconnecting power from fuse block  10 . Once door  24  is open (disconnecting bi-directional coupling mechanism  67 ) and operator assembly  36  is rotated clockwise, uni-directional coupling mechanism  64  will prevent shaft  22  from reconnecting power in fuse block  10 . Rather, the user must first perform a predetermined sequence of events by manually depressing hub  44  relative to shell  38  in order to reengage bi-directional coupling mechanism  67 . While hub  44  is depressed, operator assembly  36  can be rotated clockwise to reconnect power in fuse block  10 .  
         [0074]     The invention has been described in connection with what are presently considered to be the most practical and preferred embodiments. However, the present invention has been presented by way of illustration and is not intended to be limited to the disclosed embodiments. For example, while the present invention is applicable to fuse blocks of the type described above, it should be appreciated that the present invention is applicable to any handle-operated device that would benefit from coupling mechanisms  64  and  67 . Accordingly, those skilled in the art will realize that the invention is intended to encompass all modifications and alternative arrangements included within the spirit and scope of the invention, as set forth by the appended claims.