Patent Publication Number: US-8533884-B1

Title: Fold out ramp

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 13/454,858, filed on Apr. 24, 2012, which is a continuation-in-part of U.S. patent application Ser. No. 13/350,642, filed Jan. 13, 2012, and issued as U.S. Pat. No. 8,250,693 on Aug. 28, 2012, which is a continuation-in-part of U.S. patent application Ser. No. 13/015,439, filed Jan. 27, 2011, and issued as U.S. Pat. No. 8,132,281 on Mar. 13, 2012, the disclosures of which are expressly incorporated by reference. U.S. patent application Ser. No. 13/454,858 also claims the benefit of U.S. Provisional Application No. 61/596,117, filed Feb. 7, 2012, the disclosure of which is expressly incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The Americans with Disabilities Act (ADA) requires the removal of physical obstacles to those who are physically challenged. The stated objective of this legislation has increased public awareness and concern over the requirements of the physically challenged. Consequentially, there has been more emphasis on providing systems that enable physically challenged people to access a motor vehicle, such as a bus or minivan. 
     A common manner of providing the physically challenged with access to motor vehicles is a ramp. Various ramp operating systems for motor vehicles are known in the art. Some slide out from underneath the floor of the vehicle and tilt down. Others are stowed in a vertical position and pivot about a hinge, while still others are supported by booms and cable assemblies. The present invention is generally directed to a “fold out” type of ramp. Such a ramp is normally stowed in a horizontal position within a recess in the vehicle floor, and is pivoted upward and outward to a downward-sloping extended position. In the extended position, the ramp is adjustable to varying curb heights. 
     Fold out ramps on vehicles confront a variety of technical problems. Longer ramps are desirable because the resulting slope is more gradual and more accessible by wheelchair-bound passengers. Longer ramps are, however, heavier and require more torque about the pivot axis to be reciprocated between deployed and stowed positions. To satisfy the increased torque requirement, some fold out ramps use large electric motors, pneumatic devices, or hydraulic actuators to deploy and stow the ramp. Often, these systems cannot be moved manually in the event of failure of the power source, unless the drive mechanism is first disengaged. Some existing fold out ramps can be deployed or stowed manually, but they are difficult to operate because one must first overcome the resistance of the drive mechanism. Further, fold out ramps require a depression (or pocket) in the vehicle&#39;s vestibule floor in which to store the retracted/stowed ramp. When the ramp is deployed, the aforementioned depression presents an obstacle for wheelchair passengers as they transition from the ramp to the vestibule, and into the vehicle. 
     Another technical issue confronting fold out ramps is the variety of situations in which the ramps must operate. Depending on the use of the vehicle in which a particular ramp is installed, the ramp might be deployed to curbs of varying heights, as well as to a road surface. In addition, road crown, the inclusion of a “kneeling” feature on the vehicle, and other factors can affect the height of the vehicle floor relative to the alighting surface. Thus, the vertical distance though which a ramp must provide a transition surface can vary significantly. 
     In view of the foregoing, there is a need for a fold out ramp for a vehicle that provides a longer ramp surface to reduce the ramp angle in a variety of situations, and comprises an interior surface coplanar with the adjacent vehicle floor, and further includes a compact and efficient operating system. 
     SUMMARY 
     Various embodiments of a ramp assembly for providing a transition surface between a vehicle floor and an alighting surface are disclosed. In a first embodiment, the ramp assembly comprises a ramp portion coupled for reciprocating movement between a stowed position and a deployed position. A cam surface is disposed on the ramp, and a cam follower engages the cam surface when the ramp portion is in the stowed position to support the ramp portion. The ramp assembly further includes a panel rotatably coupled about an axis to a first end of the ramp portion. An actuator rotates a drive arm to move the ramp portion through first and second phases of a deployment motion. During the first phase, the drive arm rotates the ramp portion about the axis, which maintains a substantially fixed position. During the second phase, the drive arm moves the axis in a downward direction. 
     A second disclosed embodiment of a ramp assembly includes a ramp portion coupled for rotational movement between a stowed position and a deployed position. The ramp portion has side curb with a cam surface disposed thereon. A panel is rotatably coupled to the ramp portion about a first axis. The ramp portion further includes an elongate drive arm operably coupled to the ramp portion and extending radially from a second axis. An actuator rotates the drive arm about the second axis to move the ramp portion through a deployment motion. The deployment motion has a first phase, during which the drive arm rotates the ramp portion about the first axis, and a second phase, during which the drive arm moves the first axis from a raised position to a lowered position. The ramp assembly also includes a cam follower that engages the cam surface when the ramp portion is in the stowed position to support the ramp portion. 
     In a third exemplary embodiment, a ramp assembly has a ramp portion coupled for rotational movement between a stowed position and a deployed position, wherein the ramp portion includes a cam surface. A first panel is rotatably coupled to the ramp portion about a first axis and is rotatably associated with a second panel. The second panel reciprocates between a lowered position when the ramp portion is in the stowed position, and a raised position when the ramp portion is in the deployed position. A cam follower engages the cam surface when the ramp portion is in the stowed position to support the ramp portion. The cam follower is disengaged from the cam surface when the ramp portion is in the deployed position. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is an isometric view of an exemplary embodiment of a ramp assembly with a ramp portion in the stowed position; 
         FIG. 2  is an isometric view of the ramp assembly shown in  FIG. 1 , with the ramp portion in a neutral position; 
         FIG. 3  is an isometric view of the ramp assembly shown in  FIG. 1 , with the ramp portion in a first deployed position; 
         FIG. 4  is an isometric view of the ramp assembly shown in  FIG. 1 , with the ramp portion in a second deployed position; 
         FIG. 5  is a side view of the ramp assembly shown in  FIG. 1 , with the ramp portion in the stowed position; 
         FIG. 6  is a side view of the ramp assembly shown in  FIG. 1 , with the ramp portion in a neutral position; 
         FIG. 7  is a side view of the ramp assembly shown in  FIG. 1 , with the ramp portion in a first deployed position; 
         FIG. 8  is a side view of the ramp assembly shown in  FIG. 1 , with the ramp portion in a second deployed position; 
         FIG. 9  is a partial cross-sectional view of the ramp assembly shown in  FIG. 1 , wherein a latch mechanism is shown with the ramp portion in a first deployed position; 
         FIG. 10  is a partial cross-sectional view of the ramp assembly shown in  FIG. 1 , wherein a latch mechanism is shown with the ramp portion in a second deployed position; 
         FIG. 11  is partial isometric view of the ramp assembly shown in  FIG. 1 , with an intermediate panel and an inner panel removed; 
         FIG. 12  is a partial side view of the ramp assembly shown in  FIG. 1 , showing a drive arm when the ramp portion is in the stowed position; 
         FIG. 13  is a partial side view of the ramp assembly shown in  FIG. 1 , showing the drive arm when the ramp portion is in a neutral position; 
         FIG. 14  is a partial side view of the ramp assembly shown in  FIG. 1 , showing the drive arm when the ramp portion is in a first deployed position; 
         FIG. 15  is a partial side view of the ramp assembly shown in  FIG. 1 , showing the drive arm when the ramp portion is in a second deployed position; 
         FIG. 16  is an isometric view of a second exemplary embodiment of a ramp assembly with a ramp portion in the stowed position; 
         FIG. 17  is an isometric view of the ramp assembly shown in  FIG. 16 , with the ramp portion in a neutral position; 
         FIG. 18  is an isometric view of the ramp assembly shown in  FIG. 16 , with the ramp portion in a first deployed position; 
         FIG. 19  is an isometric view of the ramp assembly shown in  FIG. 16 , with the ramp portion in a second deployed position; 
         FIG. 20A  is a partial side view of the ramp assembly shown in  FIG. 16 , showing a linkage when the ramp portion is in the stowed position; 
         FIG. 20B  is a partial side view of the ramp assembly shown in  FIG. 16 , showing a cam surface and cam follower when the ramp portion is in the stowed position; 
         FIG. 21A  is a partial side view of the ramp assembly shown in  FIG. 16 , showing the linkage when the ramp portion is in a neutral position; 
         FIG. 21B  is a partial side view of the ramp assembly shown in  FIG. 16 , showing the cam surface and cam follower when the ramp portion is in a neutral position; 
         FIG. 22A  is a partial side view of the ramp assembly shown in  FIG. 16 , showing the linkage when the ramp portion is in a first deployed position; 
         FIG. 22B  is a partial side view of the ramp assembly shown in  FIG. 16 , showing the cam surface and cam follower when the ramp portion is in a first deployed position; 
         FIG. 23A  is a partial side view of the ramp assembly shown in  FIG. 16 , showing the linkage when the ramp portion is in a second deployed position; and 
         FIG. 23B  is a partial side view of the ramp assembly shown in  FIG. 16 , showing the cam surface and cam follower when the ramp portion is in a second deployed position. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the disclosed fold out ramp will now be described with reference to the accompanying drawings, where like numerals correspond to like elements. The described embodiments are directed to ramp assemblies, and more specifically, wheelchair ramp assemblies. In particular, several embodiments are directed to wheelchair ramp assemblies suitable for use in buses, vans, etc. Several embodiments of the present invention are directed to compact ramp assemblies for a vehicle that, when stowed, occupy a small amount of space within the vehicle floor, yet deploy to a length that effectively reduces the ramp slope encountered by the mobility impaired, thus facilitating greater independence and safety for wheelchair-bound passengers. 
     The following discussion proceeds with reference to examples of wheelchair ramp assemblies for use in vehicles having a floor, such as a bus, van, etc. While the examples provided herein have been described with reference to their association with vehicles, it will be apparent to one skilled in the art that this is done for illustrative purposes and should not be construed as limiting the scope of the disclosed subject matter, as claimed. Thus, it will be apparent to one skilled in the art that aspects of the disclosed fold out ramp may be employed with other ramp assemblies used in stationary installations, such as residential buildings and the like. The following detailed description may use illustrative terms such as vertical, horizontal, front, rear, curbside (inboard), roadside (outboard), inner, proximal, distal, etc.; however, these terms are descriptive in nature and should not be construed as limiting. Further, it will be appreciated that various embodiments of the disclosed fold out ramp may employ any combination of features described herein. 
       FIGS. 1-4  illustrate one exemplary embodiment of a fold out ramp assembly  100  (hereinafter “ramp assembly  100 ”) as it moves from a stowed position ( FIG. 1 ) through a neutral position ( FIG. 2 ), and a first deployed position ( FIG. 3 ) to a second deployed position ( FIG. 4 ). The ramp assembly  100  includes a frame  102 , a ramp portion  110 , an intermediate panel  130 , and an inner panel  150 . The frame  102  of the ramp assembly  100  is adapted to be mounted to a vehicle (not shown) having a floor, such as a bus or a van. The ramp assembly  100  is reciprocal between the stowed position, shown in  FIG. 1 , and various deployed positions, such as the ones shown in  FIGS. 3 and 4 . In the stowed position, the ramp portion  110  is located such that the ramp is disposed over the intermediate panel  130  and the inner panel  150 , and the lower surface  112  of the ramp portion faces upward and is substantially coplanar, i.e., flush, with the floor (not shown) of the vehicle. In a deployed position, the ramp portion  110  extends in a curbside and downward direction to contact an alighting surface  90 , such as a curb or road surface, thus cooperating with the intermediate panel  130  and inner panel  150  to provide a transition between the vehicle and the alighting surface  90 . 
     Although the illustrated embodiments of the ramp assembly  100  include a frame  102 , other embodiments are contemplated in which the ramp assembly  100  does not include a frame. To install such embodiments in vehicles, the ramp assembly  100  components can be attached directly to the structure of the vehicle or to a suitable structure within the vehicle, thus making a frame  102  unnecessary. Similarly, when such embodiments are installed in stationary installations, such as residential buildings and the like, the ramp assembly  100  components can be attached to the structure of the building or any other suitable structure within the building. Accordingly, embodiments of the described ramp assembly  100  that do not include a frame should be considered within the scope of the present disclosure. 
     Still referring to  FIGS. 1-4 , the ramp portion  110  includes a panel  114  constructed from well-known materials. The ramp portion  110  further includes side curbs  116  that extend upwardly from the forward and rear sides of the panel  114 . The side curbs  116  increase the strength of the ramp portion  110  and provide edge guards for the sides of the ramp portion  110 , thereby increasing the overall safety of the ramp assembly  100 . In the illustrated embodiment, the curbside end  118  of the ramp portion  110  (when the ramp is in a deployed position) is tapered to provide a smooth transition between the panel  114  and the alighting surface  90  when the ramp assembly  100  is in a deployed position, although such a feature may not be necessary, depending on the thickness of the ramp. 
     As shown in  FIGS. 1-8 , the ramp portion  110  is rotatably connected at the roadside end  120  (when the ramp portion is in a deployed position) to the curbside end  132  of the intermediate panel  130  about an axis  170 . Referring back to  FIG. 3 , the ramp portion  110  and the intermediate panel  130  of the illustrated ramp assembly  100  are connected with a single continuous hinge  172  i.e., a “piano hinge,” however, it will be appreciated that multiple hinges or any other configuration suitable for rotatably connecting the ramp portion  110  to the intermediate panel  130  and/or maintaining a rotational association therebetween can be utilized. 
     The axis  170  maintains a generally horizontal orientation so that the ramp portion  110  is rotatable about the axis to reciprocate between the stowed position and the deployed positions. In the stowed position, shown in  FIG. 1 , the ramp portion  110  extends inwardly from the axis  170  such that the ramp is at least partially disposed over the intermediate panel  130  and the inner panel  150 . When in the stowed position, the lower surface  112  of the ramp panel  114  faces upward and is oriented to be generally flush with the vehicle floor, thereby providing a surface upon which able-bodied passengers can walk while entering and exiting the vehicle. When the ramp portion  110  is in a deployed position, such as the one shown in  FIG. 4 , the ramp extends in an outward and downward direction so that the upper surface  122  of the panel  114  faces up and provides an inclined transition surface from the intermediate panel  130  to the alighting surface  90 . 
     Referring now to  FIGS. 5-8 , the inner panel  150  is configured to reciprocate between a lowered position ( FIG. 5 ), when the ramp assembly  100  is in the stowed position and a raised position ( FIG. 8 ), when the ramp assembly is in a deployed position. In the disclosed embodiment, the inner panel  150  is supported by an inner panel support  156  disposed beneath the inner panel. The inner panel support  156  includes a plurality of elongate members  158 , each elongate member having a roadside end  160  and a curbside end  162 . The roadside end  160  of each elongate member  158  forms an angle with the curbside end  162  of that elongate member that approximates the angle between the inner panel  150 , and the intermediate panel  130  when the ramp assembly  100  is in a deployed position. 
     The inner panel support  156  is configured for rotating movement at the curbside end about an axis  176 . In the illustrated embodiment, the curbside end  162  of each of the elongate members  158  is rotatably connected to the frame  102 ; however, any portion of the inner panel support can be coupled to any suitable structure to enable reciprocating movement of the inner panel  150  between the raised position and the lowered position. 
     The roadside end of the inner panel support  156  supports the inner panel  150  and is itself supported by a selectively rotatably eccentric bearing element  164 . A bearing surface  166  is disposed on a lower portion of the inner panel support  156  to engage the eccentric bearing element  164 . As the eccentric bearing element  164  is selectively rotated about its axis  180 , the bearing element engages the bearing surface  166  to raise and lower the roadside end on the inner panel support  156 . 
     As shown in  FIG. 5 , when the ramp assembly  100  is in the stowed position, the eccentric bearing element  164  is in a first position, wherein the inner panel support  156  is in a lowered position, and the inner panel  150  is disposed within the frame  102  and positioned below the ramp portion  110 . As the ramp assembly  100  moves toward a deployed position, the eccentric bearing element  164  rotates to lift the roadside end of the inner panel support  156 , thereby rotating the inner panel  150  about axis  176  to a raised position. When the inner panel  150  is in the raised position, the upper surface of the inner panel is generally horizontal and coplanar, i.e., flush, with the vehicle floor. When the ramp assembly moves from a deployed position to the stowed position, the eccentric bearing element  164  rotates back to the first position, thereby lowering the inner panel  150 . 
     It should be appreciated that the illustrated mechanism for raising and lowering the inner panel  150  is exemplary and that alternative configurations are possible. In this regard, the number and locations of the eccentric bearing elements  164  can vary. Further, the profile of the cam surface of the eccentric bearing element  164  can be modified to change the movement of the inner panel as the ramp assembly  100  reciprocates between the stowed and deployed positions. It should also be appreciated that the mechanisms are not limited to eccentric bearings and cams, but can also include any number of different linkages. In one non-limiting example, a four-bar linkage is coupled to one or more inner panel supports  156  to raise and lower the inner panel  150 . In another contemplated embodiment, one or more pins extend laterally from one or more rotatable links to support the inner panel supports. Rotation of the links moves the pins along an arcuate path to raise and lower the inner panel. While the described configurations are all adaptable to be driven by the drive assembly  230  described below, alternative configurations in which a separate actuator raises and lowers the inner panel  150  are also possible. These and other suitable configurations for raising and lowering the inner panel  150  are contemplated and should be considered within the scope of the present disclosure. 
     As shown in  FIGS. 5-8 , the intermediate panel  130  is constructed from well-known materials, and has an upper surface suitable for providing a transition surface from the inner panel  150  to the ramp portion  110  when the ramp assembly  100  is in a deployed position. As previously noted, the curbside end  132  of the intermediate panel  130  is rotatably connected to the ramp portion  110  about axis  170 . The roadside end  134  of the intermediate ramp  130  is rotatably associated with the curbside end  154  of the inner panel  150 . 
     In the illustrated embodiment, the intermediate panel  130  is supported by an intermediate panel support  136  disposed beneath the intermediate panel. The roadside end of the intermediate panel support  136  is rotatably coupled to the inner panel support  156  about an axis  184  so that as the ramp assembly  100  reciprocates between the stowed position and a deployed position, the angle between the upper surface of the inner panel  150  and the upper surface of the intermediate panel  130  changes. In an alternate embodiment, the roadside end  134  of the intermediate panel  130  is coupled directly to the curbside end  154  of the inner panel  150  with a continuous hinge, or series of hinges. These, and other suitable configurations for establishing a rotational relationship between the inner panel  150  and the intermediate panel  130 , are contemplated and should be considered within the scope of the present disclosure. 
     Still referring to  FIGS. 5-8 , the intermediate panel support  136  includes a support member  190  extending downwardly from the curbside end of the intermediate panel support. During a first phase of deployment ( FIGS. 5-7 ) the support member  190  selectively engages a latch mechanism  200  ( FIG. 11 ) that is fixedly positioned relative to the frame  102 . When the support member  190  is so engaged, the support member maintains the axis  170  about which the ramp portion  110  is connected to the intermediate panel  130  in a substantially fixed location. Although the axis  170  is maintained in a substantially fixed position, it will be appreciated that the axis  170  does move slightly as the intermediate panel  130  moves in response to the movement of the inner panel  150  between the raised and lowered positions. 
     During a second phase of deployment ( FIGS. 7-8 ), the latch mechanism  200  selectively disengages the support member  190 . With the support member  190  disengaged from the latch mechanism  200 , continued actuation of the ramp portion  110  toward a deployed position rotates the ramp portion  110  about its curbside end  118 . As a result, the axis  170  about which the ramp portion  110  is connected to the intermediate panel  130 , moves in a downward direction until the intermediate panel reaches a predetermined position. In the predetermined position, the intermediate panel  130  is supported by the inner panel support  156 . More specifically, when the intermediate panel  130  is in the predetermined position, the intermediate panel engages the elongate members  158  of the inner panel support  156 . These portions of the inner panel support  156  maintain the intermediate panel  130  in the predetermined position when the ramp portion moves through the second phase of the deployment. It should be appreciated that the present disclosure is not limited to a particular configuration for maintaining the intermediate panel in a predetermined position. In this regard, any number and types of restraints and supports can be utilized to maintain the intermediate panel  130  in the predetermined position when the ramp portion is in a deployed position, and such alternate configurations should be considered within the scope of the present disclosure. 
     Referring to  FIGS. 9 and 10 , one embodiment of a latch mechanism  200  is shown. The latch mechanism  200  includes a C-shaped catcher  202  rotatably coupled to the frame  102  to selectively retain a pin  204  that forms part of the support member  190 . The catcher  202  is rotatable between an engaged position ( FIG. 9 ) and a released position ( FIG. 10 ). In the engaged position, the pin  204  is at least partially disposed within a recess  212  formed in the catcher  202 . 
     The latch mechanism  200  further includes a pawl  206  to selectively engage a notch  208  formed in the catcher  202 . As shown in  FIGS. 9 and 10 , the pawl  206  is rotatably coupled to the frame  102  proximate to the catcher  202  and is biased to contact the pawl by a spring  210 . With the latch mechanism in the engaged position, the pawl  206  engages the notch  208  to prevent the catcher  202  from rotating toward the released position. At the same time, a pin  216  engages the catcher  202  to prevent further rotation away from the released position. Thus, as shown in  FIG. 9 , the pin  216  and the pawl  206  cooperate to lock the catcher  202  in the engaged position. 
     To unlock the latch mechanism  200 , an actuator  214  ( FIG. 11 ), which is operably coupled to the pawl  206 , temporarily rotates the pawl in a clockwise direction as viewed in  FIGS. 9 and 10  so that the pawl disengages from the notch  208  formed in the catcher  202 . With the pawl  206  disengaged from the notch  208 , the catcher  202  is free to rotate toward the disengaged position, thereby releasing the support member  190 . With the support member  190  released from the latch mechanism  200 , the curbside end  132  of the intermediate panel  130  is free to move to a lowered position as the ramp assembly  110  moves through the second deployment phase. Once the catcher  202  has rotated to the disengaged position, the actuator  214  releases the pawl  206 , and the spring  210  biases the pawl back to engage a side of the catcher. The pawl  206  remains in sliding contact with the catcher  202  until the catcher returns to the engaged position, at which time the pawl engages the notch  208  to lock the catcher in the engaged position. 
     Still referring to  FIGS. 9 and 10 , when the ramp assembly  100  moves from the deployed position toward the stowed position, movement of the ramp portion  110  drives the support member  190  upward so that the pin  204  engages the recess  212  in the catcher  202  to rotate the catcher  202  toward the engaged position. When the catcher  202  reaches the engaged position, pin  216  engages the catcher to prevent further rotation. At the same time, the spring-loaded pawl  206  rotates back to engage the notch  208  in the catcher  202 , thereby locking the latch mechanism  200  in the engaged position. In this manner, the pin  216  and the pawl  206  cooperate to retain the catcher  202  in the engaged position, thereby maintaining the axis  170 , about which the ramp portion  110  and intermediate panel  130  are connected, in a generally fixed position. 
     As previously described, the latch mechanism  200  maintains the axis  170  in a fixed position during the first deployment phase, and allows the axis  170  to move in a downward direction during the second deployment phase. It will be appreciated that other configurations to selectively maintain the location of the axis  170  are possible. In one alternate embodiment, the curbside end of the intermediate panel  130  is supported by a rotatable cam. The profile of the cam surface is such that as the ramp assembly  100  initially moves from the stowed position, the cam supports the intermediate panel  130  in a fixed position, i.e., the cam profile has a constant radius during the first deployment phase. As the ramp assembly  100  begins the second deployment phase, the cam surface disengages the intermediate panel so that the cam no longer supports the intermediate panel. As a result, the axis  170  is free to move in a downward direction during the second deployment phase, as described above. 
     In another contemplated embodiment, a Geneva drive is utilized to reciprocate one or more support elements between engaged and disengaged positions. During the first deployment phase, the support elements are in the engaged position and support the curbside end of the intermediate panel to maintain the axis  170  in a generally fixed position. During the second deployment phase, the support elements move to a disengaged position so that the axis  170  is free to move downward. The Geneva drive, which translates continuous rotation into intermittent rotary motion, allows for the support elements to be driven between two positions by the constant rotary motion provided by the drive assembly  230  described below. In this manner, the support elements are reciprocated between an engaged position (supporting the intermediate panel) and a disengaged position (not supporting the intermediate panel), wherein each position is generally fixed throughout the first and second deployment phases, respectively. 
     In yet another contemplated embodiment, a separate actuator reciprocates support elements between engaged and disengaged positions. The support elements operate in a similar manner to those described above in the embodiment that utilizes a Geneva drive; however, rather than utilize the rotary motion of the drive assembly  230  described below, a separate actuator drives the support elements between the engaged and disengaged positions. These and other configurations to selectively maintain the position of the axis  170  are contemplated and should be considered within the scope of the present disclosure. 
     Referring now to  FIGS. 1-4 , and  11 , a drive assembly  230  actuates the ramp portion  110  to reciprocate between the stowed position and a deployed position. A forward portion of the drive assembly  230  is located on the forward side of the frame  102 , and a rear portion of the drive assembly is similarly located on the rear side of the frame  102 , wherein each element of the forward portion of the drive assembly  230  corresponds to a similar element of the rear portion of the drive assembly. For the sake of clarity, the forward portion of the drive assembly  230  is described herein with the understanding that unless otherwise indicated, each element of the forward portion has a corresponding element on the rear portion of the drive assembly  230 . 
     As shown in  FIG. 11 , the drive assembly  230  includes a roadside sprocket  232  that is rotatably coupled to the roadside end of the forward side of the frame  102 , so that the axis of rotation of the roadside sprocket  232  extends in the forward/rearward direction. The drive assembly  230  also includes a curbside sprocket  234  that is rotatably coupled to the curbside end of the forward side of the frame  102  to have an axis of rotation that is substantially parallel to the axis of rotation of the roadside sprocket  232 . A drive chain assembly  236  forms an endless loop that engages the teeth of the curbside sprocket  234  and the teeth of the roadside sprocket  232 . As a result, movement of the drive chain assembly  236  along the path of the endless loop rotates the roadside sprocket  232  and the curbside sprocket  234 . 
     A drive shaft  238  is coupled to the roadside sprocket  232  and also to a motor  240  (rotary actuator) by a well-known transmission assembly  242 . The motor  240  is selectively operated to rotate the roadside sprocket  232 , thereby moving the roadside sprocket  232  and the curbside sprocket  234  via the drive chain assembly  236 . In one embodiment, a single motor  240  drives the roadside sprocket  232  of the forward portion of the drive assembly  230  and also the drive sprocket of the rear portion of the drive assembly  230 . In another embodiment, each roadside sprocket  232  is driven by a separate motor  240 . In other alternate embodiments, the drive shaft  238  connects the motor  240  to the curbside sprocket  234 , or to a separate drive sprocket that engages the drive chain assembly  236 . 
     One or more idler sprockets may be included in the drive assembly  230 . The optional idler sprockets engage the drive chain assembly  236  to redirect the drive chain assembly  236  along a predetermined path. In one embodiment, the drive chain assembly  236  includes a turnbuckle that is selectively adjustable to increase or decrease the length of the drive chain assembly  236  in order to adjust the tension of the drive chain assembly. 
     It should be appreciated that the present disclosure is not limited to the illustrated motor, which is shown as providing a rotary output, but can incorporate several other types of actuators. In one alternate embodiment, a linear actuator is utilized to drive the ramp assembly between the stowed and deployed positions. For such an embodiment, a suitable mechanism for converting linear motion into rotary motion is utilized. Non-limiting examples of such a mechanism include a rack and pinion system and a linkage. Further, the present disclosure is not limited to electric motors (actuators), but can also include hydraulic systems or any other suitable mechanism for providing a driving force to reciprocate the ramp assembly between the stowed and deployed positions. 
     As illustrated in  FIGS. 12-15 , a drive arm  250  is fixedly coupled to extend radially from the curbside sprocket  234 . The drive arm  250  includes an elongate slot  252  formed therein. A bearing element  254  is coupled to the ramp portion and is at least partially disposed within the slot  252 . As the drive assembly rotates the curbside sprocket  234 , the drive arm  250  engages the bearing element  254  to apply a moment to the ramp portion, thereby driving the ramp portion between the stowed position ( FIG. 12 ) and a deployed position ( FIG. 15 ). 
     The slot  252  and bearing element  254  configuration allows the drive arm  250  to drive the ramp portion  110  even though the axis of rotation  170  of the ramp portion is not coincident with the axis of rotation  182  of the drive arm  250 . Moreover, this configuration allows for the relative positions of the axes  170  and  182  to change as the ramp assembly  100  moves through the first and second deployment phases. It should be appreciated that alternate configurations for engaging the drive arm  250  with the ramp portion  110  are possible. In one alternate embodiment, the bearing element is disposed on the drive arm  250  and engages a slot formed in the ramp portion. This and other alternate embodiments suitable for coupling the drive arm  250  to the ramp portion to drive the ramp portion between the stowed position and a deployed position are contemplated and should be considered within the scope of the present disclosure. 
     As shown in  FIG. 11 , the eccentric bearing element  164  is coupled to the drive shaft  238  so that rotation of the drive shaft rotates the eccentric bearing element  164  to raise and lower the roadside end  152  of the inner panel  150 . As a result, rotation of the drive shaft  238  moves both the eccentric bearing element  164  and the drive arm  250  so that movement of the inner panel  150  and the ramp portion  110  are synchronized. 
     Referring to  FIGS. 1-4 , the drive assembly  230  further includes a counterbalance assembly  260 . The counterbalance assembly  260  can be any known counterbalance assembly that biases the ramp portion toward the neutral position, i.e., a position wherein the center of gravity of the ramp portion  110  is located above the axis of rotation  170  of the ramp portion, so that the center of gravity imparts no moment about the axis of rotation. By biasing the ramp portion  110  toward the neutral position, the counterbalance assembly counteracts some or all of the weight of the ramp, thereby reducing the actuating force required to reciprocate the ramp assembly  100  between the stowed position and a deployed position. As a result, a smaller motor is required, and wear on that motor is reduced. One exemplary counterbalance suitable for use with the ramp assembly is disclosed in U.S. Pat. No. 7,681,272, issued to Morris et al., which is incorporated by reference herein. It will be appreciated that the counterbalance of Morris et al. is only one exemplary counterbalance suitable for use with the presently disclosed ramp assembly, and that any number of other suitable counterbalance assemblies can by utilized in conjunction with or in place of the referenced counterbalance. 
     As previously noted, when the ramp assembly  100  is in the stowed position, the ramp portion  110  is located such that the ramp portion is positioned over the intermediate panel  130  and the inner panel  150 , and the lower surface  112  of the ramp portion  110  faces upward and is substantially coplanar, i.e., flush, with the floor (not shown) of the vehicle. When the ramp assembly  100  is in the stowed position, the intermediate panel  130  and the inner panel  150  are disposed within the frame  102 . In the exemplary embodiment shown in  FIG. 5 , when the ramp assembly  100  is in the stowed position, the intermediate panel  130  and the inner panel  150  are positioned so that the upper surfaces of the panels  130  and  150  are generally oriented such that the roadside end of each panel is lower than the curbside end of that panel. It should be appreciated that the orientation of the intermediate panel  130  and the inner panel  150 , relative to each other and to the frame  102  of the ramp assembly  100  when the ramp assembly, is in the stowed position may vary without departing from the scope of the disclosure. 
     Referring to  FIGS. 1-10 , the deployment motion of the ramp assembly  110  includes a first phase and a second phase. During the first phase, the ramp assembly  110  moves from the stowed position ( FIGS. 1 and 5 ) to a first deployed position ( FIGS. 3 and 7 ). As the ramp assembly  110  travels through the first phase, the support member  190  remains engaged with the locked latch mechanism  200 . As a result, the axis  170  about which the ramp portion  110  is coupled to the intermediate panel  130  maintains a generally fixed location; although some movement of the axis  170  occurs as the intermediate panel rotates about the pinned connection to the latch mechanism  200 . 
     To drive the ramp assembly  100  through the first phase, the motor  240  rotates the drive shaft  238  in a first direction to rotate both the drive arm  250  and the eccentric bearing element  164 . As shown in  FIGS. 12-15 , rotation of the drive arm  250  rotates the ramp portion  110  about axis  170 . At the same time, the eccentric bearing element  164  rotates to raise the roadside end  152  of the inner panel  150 , thereby moving the inner panel from a lowered position to a raised position. 
     In the disclosed embodiment, the first deployment phase ends when the ramp portion  110  has rotated through a predetermined angle about axis  170 . To determine the travel and, thus, the position of the ramp, a sensor (not shown) detects the position of the drive shaft  238 . It should be appreciated that the type and position of the sensor is not limited to one that detects the position of the drive shaft  238 , but can include sensors associated with the ramp portion  110 , other parts of the drive system, the intermediate panel, the inner panel, or any other suitable portion of the ramp assembly. 
     As shown in  FIG. 7 , when the ramp assembly  100  is located in the first deployed position at the end of the first deployment phase, the intermediate panel  130  and the inner panel  150  have generally horizontal upper surfaces. The ramp portion  110  extends outward and downward toward the alighting surface  90 . If the alighting surface  90  is a curb having sufficient height, the ramp portion  110  will contact the alighting surface, and the slope of the ramp portion  110  may be gradual enough that further deployment of the ramp assembly  100  through the second phase is unnecessary. 
     The second deployment phase begins when the actuator  214  rotates the pawl  206  to unlock the latch mechanism  200 . Unlocking the latch mechanism  200  allows the support member  190  to disengage from the catcher  202 . This, in turn, allows the curbside end  132  of the intermediate panel  130  and, therefore, axis  170  to move in a downward direction. If the ramp portion  110  is not already in contact with the alighting surface  90  when the ramp assembly is in the first deployed position and the latch mechanism is unlocked, then the weight of the ramp portion creates a moment about the bearing element  254  that tends to lift the curbside end  132  of the intermediate panel  130 . As a result, the support member  190  remains engaged with the latch mechanism  200 , and the ramp portion continues to rotate about generally fixed axis  170  until the ramp portion contacts the alighting surface  90 . 
     Once the curbside end  118  of the ramp portion  110  contacts the alighting surface  90 , either in the first deployed position or after the ramp portion has rotated through an initial part of the second deployment phase, further rotation of the drive arm  250  about axis  182  drives the bearing element  254  to rotate the ramp portion  110  about its curbside end  118 . As the ramp portion  110  rotates about its curbside end  118 , the hinge axis  170  moves in a downward direction, driving the support member  190  so that it disengages from the unlocked latch mechanism  200 . Thus, the ramp portion  110 , which rotated in a first direction relative to the intermediate panel  130  during the first deployment phase, now rotates in a second direction, opposite the first direction, relative to the intermediate panel during the second deployment phase. As a result, the ramp portion  110  and the intermediate panel  130 , which are positioned relative to each other to form an angle of greater than 180° in the first deployed position, move such that the angle formed therebetween approaches approximately 180° when the ramp assembly  100  is in the second deployed position. 
     With the ramp portion  110  and the intermediate panel  130  forming an angle of approximately 180°, the ramp portion and the intermediate panel cooperate to provide a substantially flat transition surface from the inner panel  150  to the alighting surface  90 . Although the ramp portion  110  and the intermediate panel  130  of the disclosed ramp assembly  100  form an angle of approximately 180° in the second deployed position, the distance between the vehicle floor and the alighting surface, road crown, the inclusion of a “kneeling” feature on the vehicle, the length of the ramp portion, and other factors can affect relative positions of the ramp portion and the intermediate panel in the second deployed position. Accordingly, it should be understood that the angle between the ramp portion  110  and the intermediate panel  130  in the second deployed position can vary. These and other variations in the configuration of the deployed ramp assembly are contemplated and should be considered within the scope of the disclosed subject matter. 
     In the illustrated embodiment, the second deployed position is reached when the intermediate panel  130  has achieved a predetermined angle relative to the inner panel  150 . This predetermined angle is reached when the intermediate panel  130  contacts portions of the inner panel support  156  as shown in  FIG. 8 . In this manner, the inner panel support  156  acts as a stop to limit the downward travel of the hinge axis  170  during the second phase and also provides support to the intermediate panel  130  when the ramp assembly  100  is in a fully deployed position. 
     To move the ramp assembly  100  from a deployed position to the stowed position, the motor  240  rotates the drive shaft  238  in a reverse direction. This rotation moves the drive arm  250  to raise the curbside end  132  of the intermediate panel  130  until the support member  190  engages the latch mechanism  200 . With the position of curbside end  132  of the intermediate panel  130  generally fixed by the latch mechanism  200 , further rotation of the drive arm  250  rotates the ramp portion  110  about axis  170  until the ramp portion has returned to the stowed position. As the drive arm  250  drives the ramp portion  110  toward the stowed position, the eccentric bearing element  164  rotates to lower the roadside end  152  of the inner panel  150  until the inner panel has returned to its lowered position. 
     Referring now to  FIGS. 16-23B , a ramp assembly  100  with an alternative drive assembly  230  is illustrated. The illustrated embodiment is similar to the previously described embodiment, but instead uses a linkage  270  to transfer the driving force from the motor  240  (actuator) to the ramp portion  110 . Similar to the previously described embodiment, a drive arm  272  is fixedly coupled to the curbside sprocket  234 . The drive arm  272  extends radially from the curbside sprocket  234  so that the drive arm rotates with the curbside sprocket  234  about a common axis of rotation. 
     The drive arm  272  is connected to the ramp portion  110  by a link  274  that is rotatably coupled at one end to the drive arm  272  and at the other end to the ramp portion  110 . The linkage  270  formed by the drive arm  272  and the link  274  is a scissor-type linkage that is capable of providing a driving force to the ramp portion from the motor  240 . As the drive assembly rotates the curbside sprocket  234 , the drive arm  272  drives the link  274  to apply a moment to the ramp portion, thereby reciprocating the ramp portion between the stowed position ( FIG. 20A ) and a deployed position ( FIG. 23A ). Moreover, as shown in  FIGS. 20A ,  21 A,  22 A, and  23 A, the angle between the drive arm  272  and the link  274  changes throughout the ramp motion to account for the fact that the ramp portion  110  and the drive arm  272  rotate about different axes. 
     It should be appreciated that the illustrated linkage is exemplary only and should not be considered limiting. In this regard, the position and lengths of the drive arm  272  and link  274  can vary. In addition, alternate linkage configurations that utilize one or more additional rotating or sliding links, or any other known linkage configuration can be utilized to drive the ramp portion  110 . Further, the linkage need not be coupled to a sprocket, but can be coupled to a rotary or linear actuator either directly or indirectly using a known transmission configuration. These and other alternate embodiments suitable for coupling a linkage to the ramp portion to drive the ramp portion between the stowed position and a deployed position are contemplated and should be considered within the scope of the present disclosure. 
     Referring now to  FIGS. 18 ,  19 ,  20 B,  21 B,  22 B, and  23 B, a cam surface  300  is formed on the upper edge of the roadside end  120  (when the ramp is in a deployed position) of each of the side curbs  116 . A corresponding cam follower  302  is mounted to each side of the ramp assembly  100  about an axis that maintains a fixed position relative to the vehicle. In the illustrated embodiment, the cam follower  302  is a roller bearing rotatably mounted about the axis of rotation  182  of the drive arm  272 . 
     As best shown in  FIG. 20B , when the ramp assembly  100  is in the stowed position, the cam follower  302  is engaged with the cam surface  300  to support the roadside end  120  of the ramp portion  110 . Because the cam follower  302  is secured about an axis that is fixed relative to the vehicle, the engagement of the cam follower  302  with the cam surface  300  provides added stability to the ramp panel  114 , thereby limiting movement of upward facing lower surface  112  of ramp panel  114  as passengers step on the ramp assembly  100 . As the ramp assembly  100  moves from the stowed position to the deployed position, the motion of the ramp portion  110  moves the cam surface  300  such that the cam follower  302  disengages from the cam surface. (See  FIGS. 21B ,  22 B, and  23 B.) The illustrated exemplary embodiment of the ramp assembly is described with the understanding that alternate embodiments exist within the scope of the present disclosure. In one alternate embodiment, the ramp assembly does not include a movable inner panel. Instead, the inner panel maintains a fixed position relative to the vehicle floor through the entire ramp motion. For such an embodiment, an eccentric bearing member is not required. In another alternate embodiment, the ramp assembly does not include an inner panel; instead, the intermediate panel is rotatably associated with the floor of the vehicle. 
     Another alternate embodiment of the disclosed ramp assembly uses one or more separate actuators to drive the motion of the ramp through the second deployment phase, i.e., to lower the hinged connection between the ramp portion and the intermediate panel. Moreover, the actuator or actuators are not limited to the disclosed electric motor. One of skill in the art will appreciate that the ramp assembly can be modified to use a number of different types of actuators, including linear actuators, pneumatic actuators, hydraulic actuators, and any other suitable devices for moving the ramp assembly through the deployment motion. 
     Various embodiments utilizing different control methods are also contemplated. In one embodiment, an operator activates a single switch to deploy and stow the ramp assembly  100 . When the switch is activated, the ramp assembly deploys through the first and second deployment phases regardless of the distance between the alighting surface and the vehicle floor. In one alternate embodiment, sensors detect when the ramp portion contacts the alighting surface and, based on the slope of the ramp portion at that position, a controller determines whether or not deployment through the second deployment phase is necessary. In yet another possible embodiment, the operator selectively activates one of two switches, depending on the type of alighting surface. If the alighting surface is a curb, the operator activates the corresponding switch, and the ramp portion moves through the first deployment phase until the ramp portion contacts the curb. If the alighting surface is a road, then the operator activates the second switch, and the ramp assembly deploys through the first and second deployment phases to provide a transition surface between the road and the vehicle floor. In yet another contemplated embodiment, the operator can selectively control the rotation of the drive arm  250  and the release of the latching mechanism  200  to control the ramp assembly so that the ramp portion and the intermediate panel, respectively, are at desired orientations throughout the deployment of the ramp assembly. 
     While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosed subject matter.