Abstract:
The present invention relates generally to a lay-in lug nut plate retainer. More particularly, the invention encompasses a nut plate retainer for a lay-in lug assembly nut plate. The present invention is also directed to a novel lay-in nut plate retainer which provides an alternative way to secure a nut plate to a lay-in lug body during shipping and/or the installation process. The inventive nut plate retainer has a cover with an open area and at least two legs to surround a portion of the lay-in lug and the nut plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The instant patent application claims priority to and the benefit of pending U.S. patent application Ser. No. 12/150,803, filed on May 1, 2008, titled “Lay-In Lug Nut Plate Retainer,” the entire disclosure of which application is incorporated herein by reference. 
         [0002]    The instant patent application also claims priority to and the benefit of pending U.S. Provisional Patent Application Ser. No. 61/098,838, filed on Sep. 22, 2008, titled “Retainer, Lay-In Lug Assembly Nut Plate Retainer,” the entire disclosure of which provisional application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates generally to a lay-in lug nut plate retainer. More particularly, the invention encompasses a nut plate retainer for a lay-in lug assembly nut plate. The present invention is also directed to a novel lay-in nut plate retainer which provides an alternative way to secure a nut plate to a lay-in lug body during shipping and/or the installation process. The inventive nut plate retainer has a cover with an open area and at least two legs to surround a portion of the lay-in lug and the nut plate. 
       BACKGROUND OF THE INVENTION 
       [0004]    Lay-in lugs are provided in many electrical products as the means to electrically connect service or feed phase/neutral conductors to electrical metering equipment and/or circuit protection. All lay-in lug assemblies contain a lug body, a tapped plate (referred to as the nut plate) and a wire binding screw. During a typical installation with lay-in lug assemblies, the wire binding screw and the nut plate are removed by sliding out the nut plate prior to installing a phase/neutral conductor. Sliding-out the wire binding screw and nut plate provides top down access to the lug body. This simplifies the installation of a phase/neutral conductor to the lug body. Once the phase/neutral conductor has been installed the nut plate is slide-in and the wire binding screw is driven to the necessary torque requirements. 
         [0005]    There are at least two types of nut plates used today in lay-in lug assemblies. Extruded-punched and formed plates are known to be used in existing applications. If the nut plate is of the extruded type, then the nut plate would only need to be secured in the direction of assembly (front to back with respect to the lug body). This means an additional bi-directional restraint is needed. In the extruded case, the nut plate, by default, would be constrained from top to bottom with respect to the lug body. 
         [0006]    Currently, securing the nut plate to the lug body or limiting the nut plate&#39;s slide-out motion is achieved by driving the wire binding screw into the nut plate far enough such that the screw enters the wire way of the lug body and creates pressure that keeps the nut plate in place. The nut plate retention in the assembly is dependent on the location and torque of the wire binding screw. One problem with this method is that if the screw is not properly assembled the nut plate and screw sometimes falls out during transit or during installation of the enclosure. This increases the chances for the nut plate to be misplaced, lost, or in some cases fall in unreachable places. When this happens replacement parts must be shipped or in extreme cases, finished goods replaced. This is a costly and timely burden for the manufacturer and distributor, as well as, an aggravation for the customer. 
         [0007]    This invention improves on the deficiencies of the prior art and provides an inventive lay-in lug assembly nut plate retainer. 
       PURPOSES AND SUMMARY OF THE INVENTION 
       [0008]    The invention is a novel lay-in lug assembly nut plate retainer. 
         [0009]    Therefore, one purpose of this invention is to provide a nut plate retainer for a lay-in lug assembly. 
         [0010]    Another purpose of this invention is to provide a reliable solution to use a nut plate retainer for a lay-in lug assembly. 
         [0011]    Yet another purpose of this invention is to provide a robust nut plate retainer for a lay-in lug assembly. 
         [0012]    Therefore, in one aspect this invention comprises a lay-in lug comprising: 
         [0013]    a first lug wall; 
         [0014]    a second lug wall spaced apart from and substantially parallel to said first lug wall; 
         [0015]    a nut plate supported between said first lug wall and said second lug wall; and 
         [0016]    a nut plate retainer configured to cover at least a portion of said first lug wall and said second lug wall, and substantially restrict said nut plate from moving in a direction substantially along said first and second lug walls relative to at least one open end in said lay-in lug. 
         [0017]    In another aspect this invention comprises a nut plate retainer for preventing a nut plate of a lay-in lug from moving along a wall of said lay-in lug comprising: 
         [0018]    a flexible retaining cover; 
         [0019]    a first retaining leg extending from a first section of said retaining cover, wherein said first retaining leg covers at least a portion of a first outer wall of said lay-in lug, and restricts movement of a first end of said nut plate; and 
         [0020]    a second retaining leg extending from a second section of said retaining cover, wherein said second retaining leg covers at least a portion of a second outer wall of said lay-in lug, and restricts movement of a second end of said nut plate. 
         [0021]    In yet another aspect this invention comprises a lay-in lug comprising: 
         [0022]    a first lug wall; 
         [0023]    a second lug wall spaced apart from and substantially parallel to said first lug wall; 
         [0024]    a nut plate supported between said first lug wall and said second lug wall; and 
         [0025]    a retaining means configured to cover at least a portion of said first lug wall and said second lug wall, and substantially restrict said nut plate from moving in a direction substantially along said first and second lug walls. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Although the scope of the present invention is much broader than any particular embodiment, a detailed description of the preferred embodiment follows together with drawings. These drawings are for illustration purposes only and are not drawn to scale. Like numbers represent like features and components in the drawings. The invention may best be understood by reference to the ensuing detailed description in conjunction with the drawings in which: 
           [0027]      FIG. 1  illustrates a front perspective view of a prior art lay-in lug; 
           [0028]      FIG. 2  illustrates a top-front perspective exploded view of a prior art lay-in lug; 
           [0029]      FIG. 3  illustrates a front perspective view of a lay-in lug according to an embodiment of the invention; 
           [0030]      FIG. 4  illustrates an exploded view of a lay-in lug assembly and the inventive nut plate retainer according to an embodiment of the present invention; and 
           [0031]      FIG. 5  illustrates a front perspective view of a lay-in lug assembly with the inventive nut plate retainer secured thereto according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    This invention removes the dependency between nut plate retention and the binding screw location/torque. The lay-in lug nut plate retainer secures the nut plate to the lug body independently of the torque and position of the wire binding screw. 
         [0033]    Lay-in lugs are similar to “C” or “J” type lugs, as are known, and are used to secure wires (e.g., electrical cables, wiring, tubing, etc.). Lay-in lugs are often used in electrical and similar applications to electrically connect service and/or feed phase-neutral conductors to electrical metering equipment and/or circuit protection. Lay-in lugs may be used in piping systems, such as electrical conduits and the like, to secure wires transposed vertically in a shaft, such as an electrical conduit riser. That is, lay-in lugs are used to hold (e.g., hang) wires vertically. 
         [0034]      FIG. 1  is a front perspective view of an exemplary lay-in lug  100  as is known. Lay-in lug  100  has a lug body  102  comprising a base  104  and two opposed and substantially parallel vertical lug walls  106 ,  108 . Supported between and/or atop lug walls  106  and  108  is a removable nut plate  110 , which secures a wire binding screw  112 . 
         [0035]    In use (e.g., in an installation operation), lay-in lug  100  is secured to a surface (not shown) at its base  104 . In vertical installation operations, lay-in lug  100  is secured such that the “open” ends  114  and  116  (e.g., sides of lug body  102  not dominated by a lug wall  106 ,  108 ) face substantially up and down, respectively (e.g., toward negative X and positive X, respectively). That is, lug walls  106  and  108  will be generally parallel to the direction of a gravity vector G and a secured wire  118 . Nut plate  110 , with wire binding screw  112  secured thereto, is removed from between lug walls  106 ,  108 . This provides top down (e.g., positive Z to negative Z) access to the center channel  120  of lug body  102 . Wire  118  (e.g., electrical cable, wiring, etc.) is laid in, pulled through, or otherwise transposed in the center channel  120  of lug body  102  between lugs walls  106  and  108 , generally along the X axis. Nut plate  110  is returned to placement between and/or on top of lug walls  106 ,  108  and wire binding screw  112  is torqued (e.g., screwed, driven, etc.) to secure wire  118  between base  104  and wire binding screw  112  in the Z direction. Wire  118  is, of course, further secured laterally (e.g., in the Y direction) by lug walls  106 ,  108 . 
         [0036]      FIG. 2  depicts a top-front perspective exploded view of another known lay-in lug  200 . Lay-in lug  200  is similar to lay-in lug  100  and has a lug body  202  having a lug base  204  and a pair of generally parallel, opposed lug walls  206  and  208 . Lay-in lug  200  also has a nut plate  210  (e.g., a lug cap, top, etc.) attachable to the lug body  202  for capture of a wire  118  (e.g., electrical cable, etc.) with wire binding screw  212 . As with lay-in lug  100 , lay-in lug  200  has “open” ends  214  and  216  and nut plate  210  may be moved along an axis aligned between open ends  214 ,  216  (e.g., the X axis). The nut plate  210  of lay-in lug  200  has a pair of generally parallel nut plate ears  218  and  220  and respective nut plate flanges  222  and  224 . As shown in  FIG. 2 , each of the nut plate flanges  222 ,  224  engages a respective lug body flange  226 ,  228  of the lug body  202 . Such flange arrangements, as well as similar ridged arrangements, are used to secure nut plates (e.g., nut plates  110 ,  210 , etc.) to lug bodies (e.g., lug bodies  102 ,  202 , etc.) in a vertical (e.g., Z) direction. 
         [0037]    For simplification of discussion, the XYZ axes of  FIGS. 1 and 2 , as well as  FIGS. 3-6  below, may be assumed to be fixed to the lugs  100 ,  200 ,  300 . Though lugs  100 ,  200 ,  300  may be oriented in other manners in real world applications, the lugs  100 ,  200 ,  300  are described as non-rotating within the coordinate system. For example, in the context of the present application, the Z axis always refers to the “up-and-down” direction extending through nut plates  110 ,  210 ,  310  and bases  104 ,  204 ,  304 , irrespective of whether lugs  100 ,  200 ,  300  are placed on a “ground” surface, mounted to a wall, or are otherwise differently oriented. 
         [0038]    The top-down (e.g., Z axis) access simplifies installation of wire  118  over prior “C” or “J” type lugs, but introduces a moveable and easily lost component—nut plate  110 / 210  with wire binding screw  112 / 212  attached. That is, since nut plate  110 / 210  is slideable and removable with respect to the rest of lug  100 / 200 , nut plate  110 / 210  may inadvertently slide away from lug walls  106 / 206 ,  108 / 208  in transit and/or in installation. This is especially probable and problematic during the aforementioned electrical conduit riser type installation. Since the open end  116 / 216  of lug body  102 / 202  faces downward along the X axis (e.g., towards the ground or bottom and generally in the same direction as gravity vector G), nut plate  110 / 210  is not secured in lug body  102 / 202  in the vertical (e.g., up and down, along the X axis, etc.) direction and may slide or otherwise fall out due to the force of gravity exerted on nut plate  110 / 210  and wire binding screw  112 / 212 . 
         [0039]    Efforts have been made to prevent loss of nut plate  110 / 210  and wire binding screw  112 / 212 . Generally, wire binding screw  112 / 212  is driven (e.g., screwed) through nut plate  110 / 210  far enough that wire binding screw  112 / 212  passes through center channel  120  (similarly in  FIG. 2 ) and is bound in lug base  104 / 204 . Lug Body  102 / 202  may have to be additionally machined to have a counterbore to allow wire binding screw  112 / 212  to be driven into base  104 / 204 . With the wire binding screw  112 / 212  driven to contact or otherwise engage (e.g., be limited by) base  104 / 204 , nut plate  110 / 210  is bi-directionally secured along the X axis and will not slide out as it is constrained in the Y and Z axes by the lug walls  106 / 206 ,  108 / 208  and in the X axis by the interaction of wire binding screw  112 / 212  with base  104 / 204 . Wire binding screw  112 / 212  may also engage inner vertical lug walls  106 / 206 ,  108 / 208  (e.g., as with a counterbore, etc.). 
         [0040]    These efforts fall short in that wire binding screw  112 / 212  must be used to secure nut plate  110 / 210  in the X axis. This is not useful during the installation operations described above because the wire binding screw  112 / 212  must be disengaged from the base  104 / 204  when nut plate  110 / 210  is removed to lay wire  118 . During replacement of the nut plate  110 / 210 , gravitational forces act on the nut plate  110 / 210  in the X direction and the nut plate  110 / 210  and the wire binding screw  112 / 212  may fall before the wire binding screw  112 / 212  is biased against the wire  118  and nut plate  110 / 210  interacts with the lug walls  106 / 206 ,  108 / 208  (e.g., at flanges  218 ,  220 ,  222 , and  224  and similarly in lug  100 ). 
         [0041]    This invention improves on the prior art. The lay-in lug has two spaced apart and substantially parallel lug walls. A nut plate is supported between the first lug wall and the second lug wall. A nut plate retainer exerts force on a lug wall and restricts the nut plate from moving in a direction substantially parallel to the first and second lug walls. The nut plate retainer has a flexible retaining cover and a pair of retaining legs extending from the retaining cover. Each of the retaining legs surround a portion of the outer wall of the lay-in lug and restrict movement of the nut plate. The nut plate retainer can either snap around the open end of the lug wall or along the open end wall of the nut plate. It may also clip around the nut plate and prevents its movement in a direction along the inner surfaces of the lug walls. 
         [0042]    Furthermore, the present invention generally provides an apparatus for securing nut plates in lay-in lugs. 
         [0043]      FIG. 3  illustrates a front perspective view of a lay-in lug  300 , according to an embodiment of the invention. Lay-in lug  300  may be similar to and improve on lay-in lugs  100  and  200  of  FIGS. 1 and 2 , respectively. Accordingly, similar features are not described in further detail except as necessary to elucidate embodiments of the present invention. 
         [0044]    The lay-in lug  300  has a lug body  302  comprising a lug body base  304  and two opposed and substantially parallel vertical lug walls  306 ,  308 . Supported between and/or atop lug walls  306  and  308  is a removable nut plate  310 , which secures a wire binding screw  312 . A nut plate retainer  500 , shown in  FIGS. 4 and 5 , restricts nut plate  310  from moving in direction along lug walls  306 ,  308  (e.g., along the X axis). With nut plate  310  secured by lug walls  306 ,  308  and/or restricted by nut plate retainer  500 , wire binding screw  312  biases a wire  316  in channel  318  against lug body base  304 . The lug body  302 , has a first or face wall  341 , and a second or back wall  343 . 
         [0045]    Lay-in lug  300  may be formed and/or manufactured (e.g., extruded, cast, punched, etc.) using any appropriate material. In some embodiments, base  304  and/or lug body  302  may be constructed of conductive material. In the same or alternative embodiments, base  304  and/or lug body  302  may be plated with at least one conductive material. Body  302  and base  304  may be formed as a single component or may be manufactured separately and attached to each other. 
         [0046]    Lug walls  306 ,  308  may be constructed in any manner that allows nut plate  310  to be secured between them in the Y axis as well as constrained in the Z axis, such as the configurations of  FIGS. 1 and 2 . Lug walls  306  and  308  each have respective inner surfaces  320  and  322 . Thus, nut plate  310  may be described as moveable and/or slideable in a direction substantially along inner surfaces  320 ,  322  toward and/or away from unconstrained open ends  324 ,  326 . The unconstrained open ends  324 ,  326 , have the first wall  341 , and the second wall  343 , respectively. 
         [0047]    In some embodiments, lug walls  306 ,  308  may have recessed wall channels  328 ,  330 . Nut plate  310  may sit in, be supported in, and/or be moveably and/or slideably arranged in and/or on wall channels  328 ,  330 . The wall channels  328 ,  330  may be closed channels that have some portion of lug walls  306 ,  308  overhanging edges of nut plate  310 . In other embodiments, wall channels  328 ,  330  may be open channels with no portion of lug walls  306 ,  308  above nut plate  310  in the Z axis and nut plate  310  may be secured between lug walls  306 ,  308  in a tight fitting relationship (e.g., the spacing between opposed walls  306 ,  308  is slightly smaller than the width of nut plate  310  in the Y axis). In the same or alternative embodiments, wall channels  328 ,  330  may have wall flanges  332 ,  334  that may interlock with and/or otherwise engage a portion of nut plate  310 , such as nut plate flanges  336 ,  338 . 
         [0048]    Additionally, respective outer surfaces  340 ,  342  of lug walls  306 ,  308  may have retainer channels  344 ,  346  formed thereon. In some embodiments, retainer channels  344 ,  346  may be recessed into outer surfaces  340 ,  342  of lug walls  306 ,  308 . In the same or alternative embodiments, retainer channels  344 ,  346  may have one or more raised surfaces (e.g., bumps, flanges, etc.) extending from outer surfaces  340 ,  342 . 
         [0049]    Nut plate  310  may be a removable component formed and/or manufactured of a similar material to lug body  302 . Nut plate  310  may be tapped to accommodate wire binding screw  312 . In some embodiments, nut plate  310  may have a slightly smaller length (e.g., along the X axis) than the length (e.g., along the X axis) of lug walls  306 ,  308 . In this way, nut plate  310  may allow nut plate retainer  500  to overhang and/or otherwise impinge on a wall channel  328 ,  330  and restrict movement of nut plate  310  as will be described in further details with respect to  FIGS. 4 and 5 . 
         [0050]      FIG. 4  illustrates an exploded view of a lay-in lug assembly  300 , and the inventive nut plate retainer  500 , according to an embodiment of the present invention. While  FIG. 5  illustrates a front perspective view of a lay-in lug assembly  300 , with the inventive nut plate retainer  500 , secured thereto according to an embodiment of the present invention. The inventive nut plate retainer  500 , has a top wall or cover  502 , having at least one hole or opening  512 , and an open base  508 . The nut plate retainer  500 , has a first leg or wall or panel  504 , and a second leg or wall or panel  506 . In some embodiments the outer surface of the top wall or cover  502 , could have at least one first or upper ridge or protrusion  514 . In some embodiments the outer surface of the first wall  504 , and/or the second wall  506 , could have at least one second or side ridge or protrusion  516 . It is preferred that the hole or opening  512 , is sufficiently big so as to allow the passage of the wire binding screw  312 , as more clearly shown in  FIG. 5 . 
         [0051]    As can be seen in  FIGS. 4 and 5 , that the nut plate retainer  500  is a mechanism for restricting movement of the nut plate  310  along the X axis. Nut plate retainer  500  may be a fastener such as a spring clip or circlip and may restrict movement at both open ends of the nut plate  310  along the X axis (e.g., portions of nut plate  310  oriented toward open ends  324 ,  326 ). The nut plate retainer  500 , when placed over the lay-in lug assembly  300 , may overhang at least a portion of the wall channel  328 ,  330  and/or center channel  318 . As a result, the nut plate retainer  500 , prevents the nut plate  310 , from sliding out of lug body  302 , in the unconstrained direction (e.g., positive or negative X axis). 
         [0052]    The nut plate retainer  500 , may be formed as a single component or may comprise a separate top wall  502 , retaining legs or walls  504 ,  506 , which are then secured to each other so as to form the nut plate retainer  500 . The nut plate retainer  500 , may be formed from a flexible or semi-flexible material, such as thermoplastic. As a result, the nut plate retainer  500  may fit around the lug wall  341 ,  343  in a flexible but tight fitting relationship such that a portion of plate retainer  500  (e.g., retaining legs  504 ,  506 ) exerts a force against an open end  324 ,  326  edge of a lug wall  306 ,  308  in a direction substantially along the lug wall  341 ,  343 , (e.g., along the X axis). In this way, plate retainer  500  exerts a force in one direction along the lug wall (e.g., in the positive X direction) as well as exerting a force in a substantially opposite direction along the lug wall (e.g., in the negative X direction). This secures plate retainer  500  to lug wall  341 ,  343  as well as restricting movement of the nut plate  310 . 
         [0053]    As will be understood from the description herein and the associated figures, the exact direction of the forces applied by the plate retainer  500  are not depicted. Based on the orientation and arrangement of certain portions of plate retainer  500  (e.g., retaining legs  504 ,  506 ) the resultant forces exerted on the lug body  302  and/or the nut plate  310  may differ slightly. One of skill in the art would recognize the plate retainer  500  restricts movement of the nut plate  310  as depicted in  FIGS. 4 and 5  without confining the present invention to a specific point of contact or force direction. 
         [0054]    The top wall or cover  502 , may be a flexible (e.g., thermoplastic) member, and preferably in some embodiments, it is approximately the same length as the length of an outer surface of a lug wall (e.g., outer surface  341 ,  343 ) along the Y axis (e.g., in a direction substantially perpendicular to the direction of movement of the nut plate  310 ). In alternative embodiments, the top cover or wall  502  may be slightly shorter than an outer surface of lug wall  306 ,  308 . In these embodiments, retaining legs  504 ,  506 , may flex to snap fit the nut plate retainer  500  against and/or pinch an edge (e.g., at open end  324 ,  326 , etc.) of the nut plate  310 , along walls  341 ,  343 . 
         [0055]    The retaining legs  504 ,  506  may be flexible members, and in some embodiments, approximately the same length as the width of an edge surface of a lug wall (e.g., lug walls  341 ,  343  at open end  324  or  326 ) along the Y axis (e.g., in a direction substantially perpendicular to lug walls  306 ,  308  and the direction of movement of nut plate  310 ). In alternative embodiments, the retaining legs  504 ,  506 , may be slightly shorter than an edge surface of lug wall  341 ,  343 . In these embodiments, retaining legs  504 ,  506 , may flex to snap fit plate retainer  500  against and/or pinch an edge (e.g., at the opening end  324 ,  326 , etc.) of the nut plate  310 , along walls  341 ,  343 . 
         [0056]    In operation, lay-in lug  300  is secured to a surface (not shown) at and/or by its base  304  (e.g., using mounting apparatus, etc.). In vertical installation operations, lay-in lug  300  is secured such that “open” ends  324  and  326  (e.g., sides of lug body  302  not dominated by a lug wall  306 ,  308 ) face substantially up and down, respectively (e.g., toward negative X and positive X, respectively). That is, the lug walls  304  and  306  will be generally parallel to the direction of a gravity vector G and a secured wire  316 . Nut plate  310 , with wire binding screw  312  secured thereto, is removed from between lug walls  306 ,  308 . This provides top down (e.g., positive Z to negative Z) access to the center channel  318  of lug body  302 . Wire  316  (e.g., electrical cable, wiring, etc.) is laid in, pulled through, or otherwise transposed in the center channel  318  of lug body  302  between lugs walls  306  and  308 , generally along the X axis. Nut plate  310  is returned to placement between and/or on top of lug walls  306 ,  308  by sliding nut plate  310  along wall channels  328 ,  330  and interlocking flanges  332 ,  334 ,  336 ,  338 . Wire binding screw  312  is torqued (e.g., screwed, driven, etc.) to secure wire  316  between base  304  and wire binding screw  312  in the Z direction. Wire  316  is further secured laterally (e.g., in the Y direction) by lug walls  306 ,  308 . 
         [0057]    Plate retainer  500  is clipped onto lug body  302 . Retaining legs  504 ,  506  are set onto the outer surface  341 ,  343  and the retaining legs  504 ,  506 , are secured around a portion (e.g., a portion at an open end  324 ,  326 ) of a lug wall  306 ,  308 . Retaining legs  504 ,  506 , exert a force on the wall surface  341 ,  343 , and/or retaining legs  504 ,  506 , exert a force on the end portion of the lug wall  306 ,  308 . In this way, plate retainer  500  is secured to, clipped to, pinching, etc. a lug wall  306 ,  308 . The nut plate retainer  500  thus serves as a stop which restricts the movement of the nut plate  310  along the walls  306 ,  308 . In practice, only one plate retainer  500  may be used. However, any number and/or arrangement of nut plate retainers  500  may be used. 
         [0058]    The nut plate retainer  500 , is preferably made from a material selected from a group comprising a metallic material, a composite material, a plastic material, a thermoplastic material, to name a few. 
         [0059]    The foregoing Detailed Description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Detailed Description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention. Those skilled in the art could implement various other feature combinations without departing from the scope and spirit of the invention.