Patent Publication Number: US-2023161431-A1

Title: Switch assembly with force-associated variable scroll speed and methods of use

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/862,428 filed on Jan. 4, 2018, which claims priority to and benefit of U.S. Provisional Patent Application No. 62/442,311 filed Jan. 4, 2017. Both of which are fully incorporated by reference. 
    
    
     BACKGROUND 
     Conventional capacitive sense touchscreen technologies, such as those used in smartphones and tablet devices, require significant visual engagement by a driver, which is a distraction for the driver and compromises safety. Conventional mechanical switches and knobs are less distracting because they can be safely used without requiring the driver to remove his eyes from the road, but they tend to have limited flexibility, with each switch controlling a single function or feature. 
     Thus, there is a need in the art for a switch assembly that provides sufficient feedback to the driver upon receiving driver input to avoid distracting the driver and that provides the ability to control multiple functions and/or vehicle systems with a minimal footprint. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become apparent from the following description and the accompanying exemplary implementations shown in the drawings, which are briefly described below. 
         FIG.  1    illustrates a perspective view of a switch assembly according to one implementation. 
         FIG.  2    illustrates an exploded view of part of the switch assembly shown in  FIG.  1   . 
         FIG.  3    illustrates a cross sectional view of a partially assembled switch assembly as taken through the C-C line in  FIG.  1   . 
         FIG.  4    illustrates a perspective view of the haptic exciter shown in  FIG.  2   . 
         FIG.  5    illustrates a perspective view of the housing shown in  FIG.  2   . 
         FIG.  6    illustrates a perspective view of the switch assembly shown in  FIG.  2    partially assembled. 
         FIG.  7    illustrates a perspective view of the second surface of the first PCB shown in  FIG.  2   . 
         FIG.  8    illustrates a perspective view of the second surface of the second PCB shown in  FIG.  2   . 
         FIG.  9 A  illustrates a perspective view of the second surface of the light guide shown in  FIG.  2   . 
         FIG.  9 B  illustrates a perspective view of the first surface of the light guide shown in  FIG.  2   . 
         FIG.  9 C  illustrates a cross sectional view of the light guide shown in  FIG.  2   . 
         FIGS.  10 A and  10 B  illustrate perspective views of the annular frame shown in  FIG.  2   . 
         FIG.  11    illustrates a perspective view of the membrane shown in  FIG.  2   . 
         FIG.  12    illustrates a plan view of the first surface of the touch overlay plate shown in  FIG.  1   . 
         FIG.  13    illustrates perspective view of a first surface of a light guide according to another implementation. 
         FIG.  14    illustrates a block diagram of an electrical control system according to one implementation. 
         FIG.  15    illustrates a flow diagram of instructions stored on a memory for execution by a processor disposed on the second PCB, according to one implementation. 
         FIG.  16    illustrates a flow diagram of instructions stored on a memory for execution by a processor disposed on the first PCB, according to one implementation. 
         FIG.  17    illustrates a graph of a resistance sensed by the force sensors and a corresponding force signal associated with each resistance level, according to one implementation. 
         FIGS.  18 A- 18 D  illustrate exemplary touch events and a corresponding haptic response to each touch event, according to one implementation. 
         FIG.  19 A  illustrates a perspective view of a portion of a switch assembly according to another implementation. 
         FIG.  19 B  illustrates a cross sectional view of the portion of the switch assembly shown in  FIG.  19 A  as taken through the D-D line. 
         FIG.  19 C  illustrates an exploded view of the portion of the switch assembly shown in  FIG.  19 A . 
         FIG.  20 A  illustrates a perspective view of a portion of a switch assembly according to another implementation. 
         FIG.  20 B  illustrates a cross sectional view of the portion of the switch assembly shown in  FIG.  20 A  as taken through the E-E line. 
         FIG.  20 C  illustrates an exploded view of the portion of the switch assembly shown in  FIG.  20 A . 
         FIG.  20 D  illustrates a perspective view of a portion of the switch assembly shown in  FIG.  20 A . 
         FIG.  21    illustrates a flow chart of processing a request to scroll through a menu system according to one implementation. 
         FIGS.  22 A and  22 B  illustrate exemplary graphs showing an amount of time between each discrete pressure wave being output versus a force applied. 
         FIG.  23    illustrates a schematic of a steering assembly having two switch assemblies and a display disposed adjacent to the steering assembly, according to one implementation. 
         FIG.  24    is a graph illustrating the general concept that the scroll speed can be directly proportional to the force applied to the touch overlay plate and the time that the force is applied. 
         FIGS.  25 A- 25 F  are graphs that illustrate non-limiting examples of the way that the scroll rate can vary according to the time that the force is applied to the touch overlay plate and/or the force applied to the touch overlay plate. 
     
    
    
     DETAILED DESCRIPTION 
     Various implementations include a switch assembly that includes a housing and at least two printed circuit boards (PCBs) that are disposed within the housing and are axially arranged relative to each other. One or more force sensors are disposed on one of the PCBs, and, in some implementations, the one or more force sensors receive force input received by a touch overlay plate. Signals from the force sensors are processed to determine a magnitude, acceleration, and/or location of the force input, and a haptic feedback response is received by the touch overlay plate. The haptic feedback response is based on the force magnitude, acceleration, and/or location of input, according to some implementations. Axially arranging the PCBs reduces the footprint of the switch assembly and allows for the inclusion of more electrical components in the switch assembly, according to some implementations. 
     Various implementations are described in detail below in accordance with the figures. 
     For example,  FIGS.  1 - 12    illustrate a switch assembly according to one implementation. The switch assembly  100  includes a housing  102 , a first printed circuit board (PCB)  110 , a second PCB  112 , a light guide  142 , a membrane  170 , a touch overlay plate  195 , and an annular frame  180 . 
     The housing  102  has a first wall  104  and a second wall  106  that define a chamber  108 . The second wall  106  extends axially from a radial outer edge  105  of the first wall  104 , forming a side wall. A distal edge  172  of the second wall  106  defines an opening to the chamber  108 . Longitudinal axis A-A extends through a center of the chamber  108  and the first wall  104 . 
     Two or more PCBs are arranged axially adjacent each other within the chamber  108 . In particular, a first PCB  110  is disposed within the chamber  108  adjacent the first wall  104 , and a second PCB  112  is axially adjacent and spaced apart from the first PCB  110  within the chamber  108 . A first electrical connector  114  extends from a second surface  116  of the first PCB  110 , and a second electrical connector  117  extends from a first surface  118  of the second PCB  112 . These electrical connectors  114 ,  117  are axially aligned and coupled together to allow electrical communication between the PCBs  110 ,  112 . The first PCB  110  also includes a third electrical connector  120  extending from a first surface  122  of the first PCB  110 . The third electrical connector  120  is electrically coupled with a vehicle communication bus, for example. In the implementation shown, the third electrical connector  120  is axially arranged relative to the first electrical connector  114 , but the connectors  120 ,  114  are not axially aligned. However, in other implementations, the third electrical connector  120  is axially aligned with the first electrical connector  114 . 
     The first wall  104  of the housing includes a first set of one or more projections  125  that extend inwardly into the chamber  108  in the direction of axis A-A. The first surface  122  of the first PCB  110  is disposed on a distal surface  125   a  of the first set of one or more projections  125  such that the first surface  122  is spaced apart from the first wall  104 . The first PCB  110  defines openings  124 , and the first set of projections  125  define openings  126  that are axially aligned with openings  124 . A fastener  127  is engaged through respective pairs of aligned openings  124 ,  126  to couple the first PCB  110  to the projections  125  and prevent relative movement of the first PCB  110  within the chamber  108 . Although three fasteners are shown, more or less fasteners may be selected. In other implementations, other fastening arrangements may be selected. For example, other fastening arrangements include a friction fit within the housing, snaps, clips, rivets, adhesive, or other suitable fastening mechanism. 
     A second set of projections  128  extend axially inwardly into the chamber  108  from the first wall  104  and radially inwardly into the chamber  108  (e.g., in a direction perpendicular to and toward the axis A-A) from the second wall  106 . The second set of projections  128  are spaced apart from each other. As shown in  FIG.  5   , each projection  128  includes a first rib  132  and a second rib  134 . Each rib  132 ,  134  includes a proximal edge  133  that is coupled to the second wall  106  and a distal edge  135  that is spaced radially inwardly into the chamber  108  from the proximal edge  133 . The distal edges  135  of ribs  132 ,  134  intersect and define a boss  136 . Projections  125  extend between projections  128 , but the surface  125   a  of each projection  125  is spaced apart from a surface  130  of each projection  128 . In particular, a plane that includes surface  125   a  is spaced axially between the first wall  104  and a plane that includes surface  130 . The first surface  118  of the second PCB  112  is disposed on the surfaces  130  of projections  128  such that openings  138  defined in the second PCB  112  are axially aligned with openings defined by the bosses  136 . Fasteners  137  extend through each pair of aligned openings  138 ,  136  to couple the second PCB  112  to the projections  128  and prevent relative movement of the second PCB  112  within the chamber  108 . Although four fasteners are shown, more or less fasteners may be selected. In other implementations, other fastening arrangements may be selected. For example, other fastening arrangements include a friction fit within the housing, snaps, clips, rivets, adhesive, or other suitable fastening mechanism. 
     The first PCB  110  has an outer perimeter that is shaped to fit within the chamber  108  and between the second set of projections  128 , which allows the first surface  122  of the first PCB  110  to be disposed on the surface  125   a  of projections  125 . The second PCB  112  also has an outer perimeter that is shaped to fit within the chamber  108  such that the first surface  118  of the second PCB  112  engages the ribs  132 ,  134  of the second set of projections  128 . 
     A plurality of force sensors  140  are disposed on the second surface  123  of the second PCB  112  and are spaced apart from each other. The force sensors  140  are axially aligned with respective first ribs  132  and/or second ribs  134 . This arrangement allows force to be applied in the z-direction (i.e., along central longitudinal axis A-A) toward the force sensors  140 , and the surfaces  130  of the projections  128  prevent the second PCB  112  from bending or flexing where the force sensors  140  are coupled to the second PCB  112  in response to the force applied, which prevents the force sensors  140  from being damaged. The surfaces  130  of the projections  128  also prevent axial movement of the second PCB  112  relative to the first PCB  110  and the housing  102  when force is received by the force sensors  140 . In one implementation, the force sensors  140  comprise micro electro-mechanical sensors (MEMS) that provide an output signal that corresponds with an amount of force received by the sensors. For example, the MEMS force sensors are able to detect force with as little as 2 microns of displacement. 
     The light guide  142  is disposed within the chamber  108  and includes a first surface  144 , a second surface  143  that is opposite and spaced apart from the first surface  144 , and a side edge  145  that extends between the first surface  144  and the second surface  143 . The first surface  144  of the light guide  142  faces the force sensors  140  coupled to the second PCB  112 . The light guide  142  is a plate made from a transparent or translucent material. For example, the light guide  142  may comprise acrylic or a polycarbonate material. At least one light source is disposed on the second surface  123  of the second PCB  112 . For example, in some implementations, the light source includes a light emitting diode (LED)  146 , and the side edge  145  of the light guide  142  is disposed radially adjacent the LED  146 . Light from the LED  146  travels through the side edge  145  of the light guide  142  and exits from the second surface  143  of the light guide  142 . With this system, a single light source or multiple light sources are disposed on the same side, adjacent sides, or opposing sides of the light guide  142 , and the light is directed toward the second surface  143  of the light guide  142 . However, in other implementations, the light may enter the light guide  142  through the first surface  144  of the light guide  142 . 
     In some implementations, the second surface  143 , first surface  144 , and/or side edge  145  of the light guide  142  include integrally formed micro-lenses to direct light through the light guide  142  and out of the second surface  143 . For example,  FIG.  9 C  illustrates a plurality of micro-lenses  147 , which include protrusions and/or recessed portions, on the first surface  144  of the light guide  142 . In other or further implementations, one or more light altering films are disposed on one or more of the light guide surfaces  143 ,  144  and/or side edge  145  of the light guide  142 . 
     In the implementation shown in  FIG.  9 B , the first surface  144  of the light guide  142  includes a plurality of protrusions  148  that extend axially from the first surface  144 . The protrusions  148  axially align with the force sensors  140  on the second PCB  112 . The protrusions  148  concentrate the force received by the light guide  142  onto the force sensors  140 . In one implementation, the protrusions  148  are integrally formed with the first surface  144 . However, in other implementations, the protrusions  148  may be formed separately and coupled to the first surface  144 . 
     In another implementation shown in  FIG.  13   , the first surface  144 ′ of the light guide  142 ′ is planar, and a force concentrator that is separately formed from the light guide  142 ′ is disposed between each force sensor and the first surface  144 ′ of the light guide  142 ′. Each force concentrator transfers force received by the light guide  142 ′ to the respective force sensor below the force concentrator. 
     The haptic exciter  160  provides haptic feedback to a user. For example, according to one implementation, the haptic exciter  160  is a speaker (e.g., a coneless voice coil assembly), and the haptic output is an audible or inaudible sound wave that changes the air pressure near an output surface of the speaker by propagating a plurality of pressure waves along an axis of propagation. The propagation axis is perpendicular to an output surface  161 , and in the implementation shown, is parallel to central axis A-A, which extends orthogonally to and through the surfaces  196 ,  197  of the touch plate  195 . For example, the propagation axis may be co-axial with axis A-A in some implementations. In the implementation shown in  FIGS.  1 - 12   , the output surface  161  of the haptic exciter  160  is coupled directly to the first surface  144  of the light guide  142 . Thus, at least a portion of the pressure waves propagated from the output surface  161  are directed toward and are captured by the first surface  144  of the light guide  142 , which causes vibration, or oscillation, of the light guide  142  in the z-direction. In this implementation, the first surface  144  of the light guide  142  serves as the reaction surface for the exciter  160 . The vibration of the light guide  142  is transferred to the membrane  160  and to the touch plate  195 . Thus, the haptic exciter  160  is vibrationally coupled to the inner surface  196  of the touch plate  195  because pressure waves originating from the haptic exciter  160  induce a vibratory response on the touch plate  195 . In some implementations, the haptic exciter  160  is coupled to the first surface  144  of the light guide  142  using an adhesive  162 . However, in other implementations, other suitable fastening mechanisms may be used. And, in other implementations, the output surface  161  of the haptic exciter  160  is disposed axially adjacent and spaced apart from the first surface  144  of the light guide  142 . In addition, in some implementations, the haptic exciter  160  is disposed adjacent a central portion of the first surface  144  of the light guide  142 . 
     As shown in  FIG.  4   , the haptic exciter  160  includes a flexible cable connector  164  that has a first end  165  that is coupled to a first end  166  of the haptic exciter  160  and a second end  167  that is coupled to the first surface  118  of the second PCB  112 . The flexible cable connector  164  minimizes or eliminates transmission of the vibration from haptic exciter  160  to the second PCB  112  while allowing the haptic exciter  160  to be electrically coupled to the second PCB  112 . In one non-limiting example, the flexible cable connector may be a zero insertion force (ZIF)-type connector. In alternative implementations, the haptic exciter  160  is coupled to the second PCB  112  with wires that are coupled to each via soldering or other suitable coupling mechanism. 
     In addition, the second PCB  112  defines an opening  163  through which the output surface  161  of the haptic exciter  160  extends for coupling the output surface  161  to the first surface  144  of the light guide  142 . This arrangement allows the height in the direction of axis A-A of the switch assembly  100  to be reduced, increases the energy received by the touch overlay  195  from the haptic exciter  160 , and reduces the vibrational energy transferred to the second PCB  112 . However, in other implementations, the second PCB  112  may not define opening  163 , and the haptic exciter  160  may be axially spaced apart from the second surface  123  of the second PCB  112  and disposed between the first surface  144  of the light guide  142  and the second surface  123  of the second PCB  112 . By spacing the haptic exciter  160  apart from the second PCB  112 , the vibrational energy from the haptic exciter  160  is isolated from the second PCB  112 , which allows more of the energy to be received by the light guide  142 . 
     The flexible membrane  170  extends over at least a portion the chamber  108 . A first surface  171  of the flexible membrane  170  faces the second surface  143  of the light guide  142 , and at least a portion of these surfaces  171 ,  143  are coupled together (e.g., by adhesion). A plurality of posts  173  extend axially from the distal edge  172  of the second wall  106  of the housing  102  and are circumferentially spaced apart from each other. The flexible membrane  170  defines a plurality of post openings  174  adjacent a radially outer edge  175  of the membrane  170 . The posts  173  are engaged through respective post openings  174  of the membrane  170  to prevent movement of the membrane  170  in the x-y plane (i.e., plane perpendicular to the central axis A-A). In some implementations, the surfaces  171 ,  143  are coupled together prior to the posts  173  being engaged through the openings  174 . By limiting the movement of the membrane  170  to the z-direction, the membrane  170  is able to transfer the vibration from the light guide  142  more efficiently, and the membrane  170  can prevent an x- or y-component of force incident on the switch assembly  100  from being transferred to the force sensors  140 , which prevents damage to the force sensors  140  due to shear forces. The membrane  170  may also prevent ingress of fluids or debris into the switch  100 . 
     In the implementation described above, the membrane  170  covers the opening of the chamber  108 , but in other implementations, the membrane  170  may only cover a portion of the opening of the chamber  108 . 
     The membrane  170  is formed of a flexible material that is capable of resonating in the z-direction. For example, the membrane  170  may be made of a polymeric material (e.g., polyester, polycarbonate), a thin metal sheet, or other suitable flexible material. In addition, the stiffness of the material for the membrane  170  may be selected based on the amount of resonance desired and in consideration of the load to be incident on the membrane  170 . 
     The touch overlay plate  195  has a first surface  196  and a second surface  197 . At least a central portion  201  of the first surface  196  of the touch overlay plate  195  is coupled to a second surface  198  of membrane  170 , and the second surface  197  of the touch overlay plate  195  faces in an opposite axial direction from the first surface  196  and receives force input from the user. For example, in one implementation, the second surface  198  of the membrane  170  and the central portion  201  of the first surface  196  of the touch overlay plate  195  are adhered together. 
     In some implementations, at least a portion of the second surface  197  of the touch overlay plate  195  is textured differently than the portion of the vehicle adjacent to the switch assembly  100  to allow the user to identify where the touch overlay plate  195  is in the vehicle without having to look for it. And, in some implementations, as shown in  FIG.  3   , the second surface  197  includes a non-planar surface. For example, the contour of the non-planar surface may be customized based on various applications of the assembly and/or to facilitate the user locating the second surface  197  without having to look for it. 
     In some implementations, icons are disposed on the touch overlay plate  195 , and light exiting the second surface  143  of the light guide  142  passes through the membrane  170  and the icons on the touch overlay plate  195  to illuminate the icons. For example, by providing icons on a sheet that is adhesively coupled to the touch overlay plate  195 , the icons are easily customizable for each vehicle manufacturer, and the switch assembly  100  is manufactured efficiently. 
     In some implementations, the flexible membrane  170  oscillates in the z-direction in response to receiving vibrational energy from the haptic exciter  160  via the light guide  142 , and this oscillation is transferred to the touch overlay plate  195  to provide the haptic feedback to the user. Furthermore, the haptic response of the switch assembly  100  is tunable by selecting a light guide  142 , membrane  170 , and touch overlay plate  195  that together have a certain stiffness. 
     In addition, to isolate the vibration of the light guide  142  and touch overlay plate  195  from the housing  102  and PCBs  110 ,  112  and to ensure that the light guide  142  and touch overlay plate  195  do not rotate about the central axis A-A, an interlocking mechanism is employed to couple the light guide  142  and the touch overlay plate  195 , according to some implementations. For example, as shown in  FIGS.  3 ,  6 ,  9 A,  11 , and  12   , the second surface  143  of the light guide  142  defines a second set of protrusions  157  that extend axially away from the second surface  143 . The second set of protrusions  157  includes two or more protrusions, and the protrusions  157  are spaced apart from each other. The protrusions  157  are disposed radially inward of and adjacent the side edge  145  of the light guide  142 . The flexible membrane  170  defines openings  158  through which the protrusions  157  extend. And, the first surface  196  of the touch overlay plate  195  defines recessed portions  159  that extend axially into the first surface  196 . Distal ends of the protrusions  157  extend and are seated within the recessed portion  159 . In the implementation shown in  FIGS.  9 A and  12   , there are four recessed portions  159  defined in the touch overlay plate  195  and three protrusions  157  extending from the second surface  143  of the light guide  142 . Having one or more additional recessed portions  159  allows parts to be standardized such that they can be used in different areas of the vehicle (e.g., left side or right side). However, in other implementations, the interlocking mechanism may include one or more protrusions and recessed portions. 
     In some implementations, a portion or all of the touch overlay plate  195  is comprised of a transparent or translucent material allows light to pass through the touch overlay plate  195 . For example, the touch overlay plate  195  may comprise a piece of clear, contoured glass. Other transparent or translucent materials can be used, including other crystal materials or plastics like polycarbonate, for example. The contoured nature of one side, the second side  197 , of the touch overlay plate  195  allows the user to move around their finger to find the right button location without having to initiate the switch past the force threshold. 
     The annular frame  180  includes an annular wall  181  and a side wall  182  that extends axially from adjacent an outer radial edge  183  of the annular wall  181 . The annular wall  181  includes an inner radial edge  184  that defines an opening  185  having a central axis B-B. The annular wall  181  also defines one or more post openings  186  between the inner radial edge  184  and the outer radial edge  183 . The annular frame  180  is coupled to the second wall  106  of the housing  102 . When coupled together, an inner surface  187  of the side wall  182  is disposed adjacent an outer surface  107  of the second wall  106 . A portion of the membrane  170  adjacent the outer radial edge  175  of the membrane  170  is disposed between the annular wall  181  and the distal edge  172  of the second wall  106 . Posts  173  are engaged through openings  174  defined in the membrane  170  and within respective post openings  186  of annular wall  181  to prevent movement in the x-y plane of the annular frame  180  relative to the housing  102 . When coupled, the axis B-B of the annular frame  180  is coaxial with axis A-A of the housing  102 . In the implementation shown, at least a portion of the outer radial edge  175  of the membrane  170  folds over the distal edge  172  of the second wall  106  and is disposed between the inner surface  187  of side wall  182  of the annular frame  180  and the outer surface  107  of the second wall  106 . Furthermore, protrusions  157  are disposed radially inward of the inner radial edge  184  of the annular wall  181  when the annular frame  180  is coupled to the housing  102 . 
     Fastener openings  188  are defined in the annular wall  181 , and fastener openings  177  are defined by the second wall  106  of the housing  102 . Fasteners  189  are engaged through aligned pairs of openings  188 ,  177  to couple the annular frame  180  to the housing  102 . For example, in the implementation shown in  FIGS.  1 - 12   , the annular wall  181  includes radial extensions  181   a  that extend radially outwardly from the wall  181  and define the fastener openings  188 . And, radial extensions  106   a  extend radially outwardly from the wall  106  and define fastener openings  177 . However, in other implementations, the annular frame  180  is coupled to the housing  102  using other fastening arrangements. For example, in some implementations, the annular frame  180  is coupled to the housing  102  via fasteners extending through the side wall  182  of the annular frame  180  and the outer surface  107  of the second wall  106  of the housing  102 . In other implementations, the annular frame  180  is coupled to the housing  102  using a friction fit, snaps, clips, rivets, adhesive, or other suitable fastening mechanism. 
     In certain implementations, one or more springs are disposed between the annular wall  181  of the annular frame  180  and the light guide  142  to urge the light guide  142  toward the second surface  123  of the second PCB  112 . By disposing one or more springs between the annular wall  181 , which is fixedly coupled to the housing  102 , and the light guide  142 , the one or more springs pre-load the force sensors  140 . For example, the one or more springs may pre-load the force sensors to between 1 and 5 N. In one non-limiting example, the one or more springs pre-load the force sensors to 2.8 N. For example, in the implementation shown in  FIGS.  1 - 12   , the springs include coil springs  190  that extend between a first surface  205  of the annular wall  181  and the second surface  143  of the light guide  142 . Axial depressions  206  are defined in a recessed portion  207  defined by the second surface  143  of the light guide  142  and the side edge  145  of the light guide  142 . The recessed portions  207  have a surface that is axially spaced apart from the second surface  143  of the light guide  142  in a direction toward the first surface  144  of the light guide  142 . Inward radial extensions  204  extend radially inwardly from the inner radial edge  184  of the annular wall  181 . The inward radial extensions  204  also define axial depressions  306  according to some implementations. The axial depressions  306  defined by the inward radial extensions  204  are axially aligned with the axial depressions  206  defined by the light guide  142 , and ends of each spring  190  seats in the respective axially aligned axial depression  306  of the inward radial extension  204  and the axial depression  206  of the light guide  142  to prevent movement of the coil spring  190  in the x-y plane. In addition, the membrane  170  defines spring recesses  178  that extend radially inwardly from the outer radial edge  175  of the membrane  170 , and the springs  190  extend through the recesses  178  and are spaced apart from the outer radial edge  175  of the membrane  170  so as not to interfere with the oscillation of the membrane  170 . 
     In the implementation shown in  FIGS.  19 A- 19 C , the springs are leaf springs  290 . The leaf springs  290  include a central portion  291  and leg portions  292   a ,  292   b . Leg portions  292   a ,  292   b  extend circumferentially from and radially inwardly from the central portion  291 . The second surface  243  of the light guide  242  includes a plurality of posts  293  that extend axially away from the second surface  243 , and the membrane  270  defines openings  279  through which the posts  293  extend. The central portion  291  of each leaf spring  290  is coupled to the first surface  255  of the annular wall  281  of the annular frame  280 , and the leg portions  292   a ,  292   b  engage distal ends  294  of posts  293 . When assembled, a plane that includes the first surface  255  of the annular wall  281  to which the central portion  291  of the leaf spring  290  is coupled is axially between a plane that includes the distal ends  294  of the posts  293  and a plane that includes the second surface  243  of the light guide  242 . Thus, the leg portions  292   a ,  292   b  of the leaf spring  290  are biased toward the light guide  242  and urge the first surface  244  of the light guide  242  toward the second PCB  112 . It is to be appreciated that the posts  293  may be separate from the light guide  242 , or they can be integrally formed with the light guide  242 . 
       FIG.  19 B  also shows a second set of protrusions  257 , which are similar to the second set of protrusions  157  shown in  FIGS.  3 ,  6 ,  9 A,  11 , and  12   , that extend axially away from the second surface  243  of the light guide  242 . The second set of protrusions  257  includes three protrusions, and the protrusions  257  are spaced apart from each other. The protrusions  257  are disposed radially inward of and adjacent the side edge  245  of the light guide  242 . Like the protrusions  157  described above, the protrusions  257  extend through openings in the membrane and into recessed portions defined by the first surface of the touch overlay.  FIGS.  20 A- 20 D  illustrate leaf spring  390  according to another implementation. In this implementation, the leaf spring  390  includes a central portion  391  and leg portions  392   a ,  392   b  that extend circumferentially from and radially inwardly from the central portion  391 . Each leg portion  392   a ,  392   b  also includes an arcuate portion  393  having an apex  394  that is within a plane that is spaced apart from a plane that includes the central portion  391 . The central portion  391  is coupled to the first surface  355  of an annular wall  381 , and the apex  394  of each arcuate portion  393  abuts the second surface  343  of the light guide  342 . The arcuate portion  393  maintains a minimum axial spacing between the second surface  343  of the light guide  342  and the first surface  355  of the annular wall  381 . 
     At least a portion of the leaf spring  390  is coupled to the annular frame  380 . The inner radial edge  384  of the annular wall  381  includes one or more resilient tabs  375  that extend axially in a first direction (i.e., in a direction away from and orthogonal to the first surface  355  of the annular wall  381 ) from the inner radial edge  384 . Each resilient tabs  375  has a shoulder  376  that extends radially outwardly from the tab  375  toward the first surface  355  of the annular wall  381 . Each shoulder  376  is axially spaced apart from the first surface  355  of the annular wall  381 . The side wall  382  of the annular frame  380  also includes one or more tabs  378  that extend radially inwardly from an inner surface  383  of the side wall  382 . The one or more tabs  378  are axially spaced apart from the first surface  355  of the annular wall  381 . The first surface  355  of the annular wall  381  includes one or more protrusions  379  that extend axially in the first direction from the first surface  355 . A radially outer edge  331  of the central portion  391  of the leaf spring  390  is urged axially between tabs  378  and the first surface  355  of the annular wall  381 , and a radially inner edge  332  of the central portion  391  is urged against the resilient tabs  375 , which causes the resilient tabs  375  to bend radially inwardly as the leaf spring  390  passes by the shoulders  376  and is disposed between the shoulders  376  and the first surface  355  of the annular wall  381 . Also, a concave surface of each arcuate portion  393  is positioned to face axially toward the first surface  355  of the annular wall  381  such that the apex  394  faces away from the first surface  355 . The leaf spring  390  defines one or more openings  377  that align with the one or more protrusions  379 , and the protrusions  379  extend through the openings  377  when the edges  331 ,  332  are disposed between the tabs  375 ,  378  and the first surface  355  of the annular wall  381 . The tabs  375 ,  378  hold the leaf spring  390  axially and radially adjacent the annular frame  380 , and the protrusions  376  engaged through the openings  377  prevent the leaf spring  390  from circumferential movement relative to the annular frame  380 . 
     In other implementations, the leaf spring  290 ,  390  is overmolded with a portion of the annular frame  280 ,  380  over the central portion  291 ,  391  thereof. And, in some implementations, the spring  290 ,  390  may be adhered to, snapped to, or otherwise fastened to the annular frame  280 ,  390 . 
     In addition, according to various implementations, the leaf spring  290 ,  390  may comprise a spring steel plate. 
     The central portion  201  of the touch overlay plate  195  is disposed within the opening  185  defined by the inner radial edge  184  of the annular wall  181  and is coupled to the membrane  170 , as described above. As shown in  FIG.  12   , the first surface  196  of the touch overlay plate  195  defines a recessed portion  199  adjacent an outer radial edge  200  of the touch overlay plate  195 . The recessed portion  199  and an outer radial edge  202  of the central portion  201  of the first surface  196  further define a plurality of depressions  203  (or grooves) that extend axially from the first surface  196  of the central portion  201  to the annular recessed portion  199  and radially inwardly from the outer radial edge  202 . To prevent the touch overlay plate  195  from contacting the annular frame  180 , the depressions  203  are spaced radially inwardly of the radial extensions  204  of the annular wall  181  of the annular frame  180 . In addition, the distance T T  between the surface of the annular recessed portion  199  and the surface of the central portion  201  is greater than a thickness T A  (as measured in the z- or axial direction) of the annular wall  181 . And, a diameter (or width W T ) of the second surface  197  of the touch overlay plate  195  is greater than a diameter (or width W A ) of the annular wall  181  such that the touch overlay plate  195  hides the annular wall  181  when the assembly  100  is viewed from the second surface  197  of the touch overlay plate  195 . 
     In some implementations, such as those described above, the distal edge  172  of the second wall  106  of the housing  102 , the annular frame  180 , the light guide  142 , and the outer radial edge  200  of the touch overlay plate  195  are generally circular. However, in other implementations, these portions of the switch assembly may have a non-circular shape, such as triangular, rectangular, or other suitable polygonal shape. 
     In other implementation, the switch assembly includes just one PCB on which the force sensors are disposed. In such implementations, the circuitry required to operate the switch fits on the one PCB. 
     In addition, in other implementations, the switch assembly may include just one PCB and one force sensor for applications that require output from one force sensor (output that is not position specific). 
     In some implementations, the switch assemblies described above are mountable within a vehicle. For example, the switch assemblies are mountable to a steering wheel, such as to the bevel or hub of the steering wheel, for use in controlling various vehicle systems. In other examples, the switch assemblies are mountable to a vehicle door, gear shifter, dashboard, or any portion of the vehicle where input can be provided and used to control one or more vehicle systems. 
     For example, in some implementations, such as those described above, the housing is coupled to a trim piece in the vehicle instead of a frame or support portion of the vehicle, which isolates the vibration from the haptic exciter from other portions of the vehicle. This arrangement also allows the gap between edges of the trim piece and the outer edge of the assembly to be minimized because the trim piece can move with the assembly. To couple the housing to the trim piece (or other portion of the vehicle), bosses  208  that extend radially outwardly from the outer surface of second wall are aligned with openings defined adjacent the portion of the vehicle to which the switch assembly is being coupled. A fastener is engaged through the aligned openings to secure the assembly to the vehicle. 
       FIG.  14    illustrates a block diagram of the electrical control system  500 , according to one implementation. The electrical control system  500  may include a computing unit  506 , a system clock  508 , and communication hardware  512 . In its most basic form, the computing unit  506  includes a processor  522  and a system memory  523  disposed on the second PCB  112 . The processor  522  may be standard programmable processors that perform arithmetic and logic operations necessary for operation of the electrical control system  500 . The processor  522  may be configured to execute program code encoded in tangible, computer-readable media. For example, the processor  522  may execute program code stored in the system memory  523 , which may be volatile or non-volatile memory. The memory  523 , which can be embodied within non-transitory computer readable media, stores instructions for execution by the processor  522 . The system memory  523  is only one example of tangible, computer-readable media. In one aspect, the computing unit  506  can be considered an integrated device such as firmware. Other examples of tangible, computer-readable media include floppy disks, CD-ROMs, DVDs, hard drives, flash memory, or any other machine-readable storage media, wherein when the program code is loaded into and executed by a machine, such as the processors  522 ,  532 , the machine becomes an apparatus for practicing the disclosed subject matter. 
     In addition, the processor  522  is in electrical communication with the force sensors  140 . In some implementations, the system  500  further includes a transceiver that is in electrical communication with the processor  522  and one or more vehicle systems. And, in some implementations, the system  500  further includes a power amplifier  530  that is in electrical communication with the processor  522  and the haptic exciter  160 . 
     However, in other implementations, the system  500  includes two or more processors and/or memories, and the processors and/or memories may be disposed on the first and/or second PCBs. And, in other implementations, the assembly includes one or more PCBs on which one or more force sensors, one or more memories, and one or more processors are disposed. 
     Aspects of the present invention are described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to implementations of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
       FIG.  15    illustrates a flow diagram of instructions stored in the first memory  523  for execution by the first processor  522  according to one implementation. The instructions cause the first processor  522  to: (1) receive a signal from each of the one or more force sensors  140 , the signal being associated with a force received by each of the force sensors  140 , as shown in step  1102 , (2) determine a force magnitude and/or x,y location associated with the received force signals, as shown in step  1104 , and (3) communicate the force magnitude and/or x,y location to the second processor  532  disposed on the first PCB  110 , as shown in step  1106 . Having the force sensors  140  in close proximity to the first processor  522  that initially processes the signals from the force sensors  140  reduces the likelihood of noise in the signals. 
       FIG.  16    illustrates a flow diagram of instructions stored in the second memory  533  for execution by the second processor  532 . The instructions stored in the second memory  533  cause the second processor  532  to: (1) receive the force magnitude and/or x,y location from the first processor  522 , as shown in step  1202 , (2) identify a haptic feedback response associated with the force magnitude and/or x,y location, as shown in step  1204 , (3) communicate the haptic feedback response to a haptic exciter  160 , as shown in step  1206 , and (4) communicate the x,y location and/or the force magnitude to another vehicle system, as shown in step  1208 . The switch assembly  100  according to one implementation may be configured for controlling up to  32  functions. 
     The force sensors  140  each receive a portion of the force applied to the touch overlay  195 , and the force received by each sensor  140  is processed by the first processor  522  to determine a position and magnitude of the force applied. The position of the force is determined by the portion of the force received by each force sensor  140  and their known location relative to each other. For example, in the implementation shown in  FIG.  17   , the force received by each sensor  140  (shown on the x-axis) is associated with a resistance (shown on the y-axis). The position of the applied force is measured in either one dimension (e.g., the x- or y-dimension) or two dimensions (e.g., the x- and y-directions or plane), and the magnitude of the force is measured in the z-direction. In the implementation shown in  FIGS.  1 - 12   , which has four force sensors  140 , the position of the force is determined by quad-angulation of the force signals received from each sensor  140 . In further or alternative implementations, the position of the force is determined by tri-angulation using three force sensors. For example, if one of the four force sensors  140  fails during operation, the location is determined by tri-angulation using the force signal received from the remaining three sensors  140 . 
     The switch assembly  100  also senses the time that a force is applied at a particular location. For example, the memory  523  may store processing parameters, such as a range of force over time values that indicate an input signal has been received. Input received outside of the range may be ignored by the system as unintentional contact with the switch assembly  100 . For example, the upper limit of the input range may be  10 N of force applied for 20 seconds or less. Furthermore, the switch assembly  100  may also set a force threshold for locking an input area (e.g., 2.5 N) around a location of force input and a second, higher threshold for a force received within the input area for enabling the system  100  (e.g., 3 N). Additional description of force thresholds and virtual input areas are provided in U.S. Patent Application Publication Nos. 2015/0097791 and 2015/0097795, both published Apr. 9, 2015, which are included in the Appendix to this application. 
     In response to the magnitude, location, and/or duration of the applied force meeting the input parameters, the switch assembly  100  generates a haptic and/or audible feedback signal responsive to the detected force. For example, the haptic and/or audible feedback signal may be proportional to the force received. As shown in  FIGS.  18 A-D , each touch event (e.g., touch-down shown in  FIG.  18 A , lift-off shown in  FIG.  18 B , end of list shown in  FIG.  18 C , and hold-down shown in  FIG.  18 D ) is initiated by a different user interaction (e.g., different force value and/or duration of the touch) and, accordingly, can trigger different haptic and/or audible output feedbacks provided to the user. Exemplary haptic and/or audible feedback signal responses are described in U.S. Patent Application Publication Nos. 2015/0097794 and 2015/0097793, both published Apr. 9, 2015, which are included in the Appendix to this application. 
     The drawings illustrate the switch assembly as viewed in an upright orientation in which the central longitudinal axis A-A is vertically oriented. However, the orientation shown in the drawings should not limit how the switch assembly may be oriented within the vehicle. For example, in various implementations, the switch assembly is disposed in the vehicle such that the central longitudinal axis A-A is horizontal or has a horizontal component relative to the ground. 
     In certain implementations, the switch assembly  100  allows a user to control scrolling through a list of menu options made available by a menu system. As used herein, “menu system” refers to any system that includes a list of one or more options, and “menu options” refer to the options made available by the menu system. When the menu system has a relatively long list of menu options, the switch assembly  100  provides a force scrolling feature, which allows the user to apply more force to the touch overlay plate  195  to scroll more quickly through the menu options or apply less force to scroll less quickly. The haptic feedback corresponds to the speed of scrolling through the menu options to give the user haptic feedback as menu options are scrolled through. Thus, the speed of scrolling and the frequency at which the pressure waves are output by the haptic actuator  160  are proportional to the amount of force applied. 
     To activate the force scrolling feature, a force scroll delay is set for the switch assembly  100 , according to some implementations. For example, the processor activates force scrolling in response to detecting an initial threshold amount of force on the force sensors  140  for a minimum elapsed time. 
     The initial threshold amount of force and the minimum elapsed time may be set during manufacturing or changed later by the end user or a manufacturer of other equipment that incorporates the switch assembly. 
     Once activated, the force scrolling feature allows the user to scroll through a plurality of menu options with one push and one lift off to scroll to or near the menu option to be selected, instead of having to apply sequential pushes and lift offs to the touch overlay plate  195  to scroll through each option. Once the user approaches the menu option to be selected, the user can push and lift off more quickly to scroll through the menu options one by one until the menu option to be selected is reached. 
     For example, as shown in  FIG.  24   , the general concept that the scroll speed can be directly proportional to the force applied to the touch overlay plate  195  and the time that the force is applied. In other words, as the force applied increases over time, the scroll speed  2402  increases proportionally over time. The relationship may be linear (as shown in  FIG.  24   ), exponential, or have any other relationship such that the scroll speed increases over time as the force applied to the touch overlay plate  195  increases. It is also to be appreciated that the scroll speed decreases as the force applied to the touch overlay plate  195  decreases over time.  FIGS.  25 A- 25 C  illustrate the relationship of scroll speed over time given a constantly increasing force, Force 1 , where Force 1  is initially over a given threshold and Force 1  is constantly applied and increases over time. In some instances, as shown in  FIG.  25 A , the scroll speed continues to increase as long as the force, Force 1 , is applied to the touch overlay plate  195 . In other instances, as shown in  FIG.  25 B , the scroll speed may reach a maximum scroll speed (associated with the force being applied to the touch overlay plate being at or above a threshold), regardless of the force being applied. When the force being applied to the touch overlay plate  195  decreases, the scroll speed may proportionally drop below the maximum scroll speed. In yet other instances, as shown in  FIG.  25 C , regardless of the force applied to the touch overlay plate  195  (so long as the force applied is over the threshold force, there may be a delay period before the scrolling begins. Once the scrolling begins, it may begin and accelerate at a first rate (slow scroll) for a period of time, and then accelerate more rapidly to faster scroll speeds (fast scroll). This may occur as the applied force stays constant over time and/or as the applied force increases over time. Similarly, as the force applied decreases, the scroll speed may decrease proportional to the applied force, or in discrete steps. Also, as the force is applied to the touch overlay plate  195 , there may be discrete periods of scroll speed. For example, as shown in  FIG.  25 D , there may be a delay period after application of the initial force and as the force increases. After the initial period, there may be a period where the scroll speed jumps to a set constant scroll speed. Then, there may be additional period where the scroll speed continues to jump to set discrete constant values as the applied force is maintained and/or continues to increase. As with the above, as the applied force is decreased the scroll speed may “step down” in discrete steps with periods of constant speed at each step.  FIGS.  25 E and  25 F  illustrate other embodiments of force scrolling. In  FIG.  25 E , scrolling begins and slowly accelerates as soon as the applied force exceeds a threshold. It then reaches a time, t 1 , where it accelerates more rapidly as the force is maintained and/or increased over time. The scrolling may continue to accelerate as the force is maintained and/or increased over time. Similarly, the scroll rate may decrease as the force applied is lessened. In  FIG.  25 F , the scroll rate begins at an initial scroll speed regardless of the force applied to the touch overlay plate  195  (so long as the force applied is greater than a threshold force). If the applied force is maintained and/or increased, the scroll speed jumps to another scroll rate that is faster than the initial rate. If the force is maintained and/or increase, the scroll rate may continue to speed up in discrete steps. Similarly, the scroll rate may decrease as the force applied is lessened. 
     It is to be appreciated that  FIGS.  25 A- 25 F  illustrate non-limiting examples of the way that the scroll rate can vary according to the time that the force is applied to the touch overlay plate and/or the force applied to the touch overlay plate. In general, every force applied to the touch overlay plate (so long as the force is above a minimum threshold) has an associated scroll speed. However, if an excessive amount of force is initially applied to the touch overlay plate (i.e., a “hard touch”), it may be desired that the scroll speed does not accelerate to the speed associated with the touch applied, but rather the scroll speed initially may be delayed or be a scroll speed associated with a lower applied force for at least an initial period of time. The speed may then ramp up to the scroll speed associated with the force that is being applied after the initial period of time lapses. 
       FIG.  21    illustrates a flow chart of the operation of the force scrolling function according to some implementations. The steps in the flow chart are stored on the memory  523  and executed by the processor  522  in certain implementations. Beginning at step  2102 , a force signal is received from the force sensors  140 . Then, at step  2104 , a force magnitude associated with the force signal is determined. At step  2106 , the force magnitude is compared to an initial threshold force amount to determine if the initial threshold amount is exceeded. Next, in step  2108 , an elapsed time that the force magnitude exceeds the initial threshold force amount is measured, and in step  2110 , the elapsed time is compared to a minimum elapsed time. 
     In response to the elapsed time being greater than the minimum elapsed time, a haptic feedback control signal for communicating to the haptic actuator is generated, as shown in step  2112 . The haptic feedback control signal causes the haptic actuator  160  to propagate a plurality of pressure waves with a propagation frequency that is proportional to the force magnitude. The propagation frequency refers to the number of times per second the haptic actuator  160  propagates each discrete, sequential pressure wave. The frequency of each pressure wave is a pressure wave frequency and may be set during manufacturing or changed later by the end user or a manufacturer of other equipment that incorporates the switch assembly. In addition, or as an alternative, the pressure wave frequency may be selected from a plurality of pressure wave frequencies based on the signal received by the switch assembly  100 . 
     The haptic feedback may include inaudible pressure waves causing a vibrational output to the user, audible pressure waves causing an audible output to the user, and/or a pattern of inaudible and audible pressure waves that are alternately propagated. And, in implementations in which two or more switch assemblies  100  are coupled to the steering assembly, the haptic feedback may include inaudible and/or audible pressure waves propagated from another switch assembly  100  other than the one to which force was applied by the user. The inaudible pressure waves are pressure waves having a frequency that is below the audible frequency range for humans, and the audible pressure waves are pressure waves having a frequency that is within the audible frequency range for humans. In addition, the audible pressure waves are selected from one or more stored audio output signals. The haptic actuator in certain implementations is a speaker, and the speaker does not make any audible noise when outputting the inaudible pressure waves. For example, the speaker may include a standard voice coil assembly speaker with the cone removed. 
     In addition, a scroll control signal for communicating to the menu system is generated, as shown in step  2114 . The menu system has a plurality of menu options, and the scroll control signal causes the menu system to scroll through the plurality of menu options at a scroll frequency associated with the propagation frequency. The scroll frequency is the same as the propagation frequency in some implementations. 
     Also, in some implementations, the propagation frequency is selected from a range of frequencies between a minimum frequency and a maximum frequency. A difference between the maximum frequency and the minimum frequency is proportional to a number of menu options of the menu system. For example, the slope of the control frequency at which the pressure waves are output versus the force, and the rate at which scrolling between menu options occurs can be increased or decreased based on the number of menu options and/or based on user or manufacturing preferences. For example, as shown in  FIG.  22 A , the graph on the left has an initial threshold amount of force of 1 Newton and an initial scroll rate of 0.4 seconds between haptic outputs. The scroll rate decreases to 0.1 seconds with a force of 10 Newtons.  FIG.  22 B  illustrates another graph for which the initial threshold amount of force is 3 Newtons and the initial scroll rate is 0.3 seconds. The scroll rate decreases to 0.1 seconds with a force of 8 Newtons. As used herein, “scroll rate” refers to the amount of time between haptic outputs and scrolling between menu options. 
     As shown in  FIG.  23   , the switch assembly  100  is associated with a display  1000  for displaying the plurality of menu options  1002 . The display  1000  is disposed adjacent the switch assembly  100  in  FIG.  23   , such as on a dashboard or center console in the vehicle, but in other implementations, the display may be part of the switch assembly or spaced further away from the switch assembly  100 . 
     The menu system includes any system that provides a list of options that can be selected by the user. A non-limiting list of exemplary menu systems includes volume control for an audio system or device, a dropdown list, and an alpha-numeric list. 
     The force scrolling functionality described above has been described with respect to the switch assemblies shown in the accompanying figures. However, the force scrolling functionality may be used with any force sensing system that controls scrolling through a menu system. The force sensing systems include, for example, one or more force sensors, a touch plate that transfers force received by a touch surface of the touch plate to the one or more force sensors, a haptic actuator, a memory, and a processor in electrical communication with the memory, the one or more force sensors, and the haptic actuator. The memory stores the instructions and the processor executes the instructions as described above to provide haptic feedback to the user of the switch assembly as the user scrolls through a menu system. 
     The terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The implementation was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various implementations with various modifications as are suited to the particular use contemplated.