Abstract:
A wheelchair lift assembly having first and second attachment arm assemblies ( 26   a  and  26   b ) is disclosed. The first and second attachment arm assemblies extend between a reciprocating platform ( 24 ) and a lift platform ( 28 ). The lift platform is movable between at least a raised position and a lowered position. The lift platform being held in a substantially horizontal first plane as the lift platform is moved between at least the raised and lowered positions. A support device ( 20 ) coupled to one of the first and second attachment arm assemblies for supporting one of the first and second attachment arm assemblies and maintaining the lift platform in a second plane substantially parallel to the first plane if at least a portion of the other of the first and second attachment arm assemblies fail.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/243,331, filed Oct. 25, 2000, the disclosure of which is hereby expressly incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to wheelchair lifts and, more particularly, to a support assembly for a lift arm of a motor vehicle wheelchair lift.  
         BACKGROUND OF THE INVENTION  
         [0003]    The Americans with Disabilities Act (ADA) requires the removal of physical obstacles to those who are physically challenged. Included within the scope of the ADA are motor vehicles, such as trains and buses. Specifically, new, used or remanufactured buses shall comply with the applicable provisions of the statute. One such provision requires that deployed platforms, when occupied, shall prevent the platform from dropping an occupant in the event of a single failure of any load-carrying component. Thus, the ADA mandates that all load carrying components of a wheelchair lift cannot have single points of failure.  
           [0004]    Currently, there are a wide variety of wheelchair lifts available for motor vehicles. One such lift is adapted to be reciprocally mounted within a luggage compartment or stairwell of a bus or train. Such a lift includes a reciprocating platform mounted within the vehicle and a lift platform selectively actuatable between at least a raised and lowered position. The lift platform is hingedly attached to the reciprocating platform by two sets of hinge arm assemblies. The hinge arm assemblies are located on opposite sides of the lift platform and include a support arm and a balance arm. One end of the support and balance arms of each hinge arm assembly is pinned to opposite sides of the lift platform, while the other ends of the hinge arm assemblies are pinned to opposite sides of the reciprocating platform. As attached, the hinge arm assemblies reciprocate the lift platform between the raised position and the lowered position. Although such a lift is effective at accommodating wheelchair access into and out of a motor vehicle, it is not without its problems.  
           [0005]    One of the major problems associated with currently available wheelchair lifts is the design of the hinge arm assemblies. Specifically, if one of the pins attaching the support arm to the lift platform fails, the lift platform would pivot about the pin attaching the balance arm to the lift platform, thereby potentially injuring a person located on the lift platform. This is due in part to the attachment location of the hinge arm assembly to the lift platform relative to the center of gravity of the lift platform.  
           [0006]    Such a wheelchair lift is not only dangerous, it also fails to comply with the prohibition of the ADA regarding single point failure of any load carrying component. Further, such wheelchair lifts are also not in compliance with recent proposed revisions to the ADA establishing even more stringent requirements with at least regard to the single point of failure provision. Moreover, the proposed revisions to the ADA are also applicable to existing wheelchair lifts. Therefore, existing wheelchair lifts must be retrofitted.  
           [0007]    For at least the foregoing reasons, there exists a need for a wheelchair lift that includes a redundant support in the event of a failure of a portion of the lift, wherein the redundant support complies with the ADA requirements, is economical to install and maintain, and may be easily retrofitted into existing wheelchair lifts.  
         SUMMARY OF THE INVENTION  
         [0008]    In accordance with certain embodiments of the present invention, a wheelchair lift assembly is provided. The wheelchair lift assembly includes first and second attachment arm assemblies extending between a reciprocating platform and a lift platform. The lift platform is movable between at least a raised position and a lowered position. The lift platform is held in a substantially horizontal first plane as the lift platform is moved between at least the raised and lowered positions. The wheelchair lift assembly further includes a support device coupled to one of the first and second attachment arm assemblies, where the support device supports one of the first and attachment arm assemblies and maintains the lift platform in a second plane substantially parallel to the first plane if at least a portion of the other of the first and second attachment arm assembly fails.  
           [0009]    In accordance with further aspects of this invention, the support device includes a bracket extending between an upper arm and a lower arm of one of either the first or second attachment arm assembly. In another aspect of this invention, the support device includes a second bracket extending between an upper arm and a lower arm of the other of the first or second attachment arm assembly.  
           [0010]    In accordance with still yet another aspect of this invention, the support device includes a U-shaped first bracket pinned to one of an upper or lower arm of the first or second attachment arm assembly. In accordance with still yet another aspect of this invention, the support device includes a U-shaped bracket pinned to one of an upper or lower arm of each of the first and second attachment arm assemblies. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The foregoing aspects and many of the attendant advantages of this invention will become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0012]    [0012]FIG. 1 is a perspective view of a wheelchair lift assembly having a support assembly formed in accordance with one embodiment of the present invention;  
         [0013]    [0013]FIG. 2 is a side planar view of a wheelchair lift having a support assembly formed in accordance with one embodiment of the present invention;  
         [0014]    [0014]FIG. 3 is a cross sectional view of the support assembly formed in accordance with one embodiment of the present invention taken substantially through Section  3 - 3  of FIG. 2;  
         [0015]    [0015]FIG. 4 is a partial perspective view of a wheelchair lift having a support assembly formed in accordance with another embodiment of the present invention;  
         [0016]    [0016]FIG. 5 is a cross sectional end view of the support assembly of FIG. 4;  
         [0017]    [0017]FIG. 6 is a partial perspective view of a wheelchair lift having a support assembly formed in accordance with yet another embodiment of the present invention; and  
         [0018]    [0018]FIG. 7 is a cross-sectional view of the support assembly formed in accordance with the embodiment of FIG. 6 and taken substantially through Section  7 - 7  of FIG. 6. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]    [0019]FIGS. 1 and 2 illustrates one embodiment of a support assembly  20  formed in accordance with the present invention. The support assembly  20  is designed to be used with a wheelchair lift  22 , such as the wheelchair lift disclosed in U.S. Pat. No. 5,110,252, issued to Aoki, the disclosure of which is hereby expressly incorporated by reference. For clarity, the vehicle to which the wheelchair lift  22  can be installed has not been illustrated. Further, although the support assembly  20  is illustrated as fastened to a reciprocating platform lift, other types of wheelchair lifts, such as wheelchair lifts mounted in a stairwell of a vehicle, are also within the scope of the present invention.  
         [0020]    The wheelchair lift  22  includes a reciprocating platform  24 , a pair of attachment arm assemblies  26   a  and  26   b,  and a lift platform  28 . The reciprocating platform  24  is slidably attached to a pair of support rails (not shown) located within a vehicle (not shown). The support rails are in turn fastened to a support structure, such as a passenger floor or stairwell, of the vehicle by well known fasteners, such as bolts.  
         [0021]    The reciprocating platform  24  is adapted to slide within the support rails between a stowed position, wherein the wheelchair lift  22  is received within a stowage compartment located within the vehicle, and a deployed position, wherein the lift platform  28  is adapted to receive a wheelchair, as is described in greater detail below.  
         [0022]    The attachment arm assemblies  26   a  and  26   b  are hingedly attached to one end of the reciprocating platform  24 . As attached, the attachment arm assemblies are able to reciprocate the lift platform  28  between a lowered position, an intermediate position, and a raised position, as is well known in the art. In the lowered position, the lift platform  28  is located adjacent a curbside or loading platform. In this position, a wheelchair may be rolled on or off of the lift platform  28 . In the intermediate position, the lift platform  28  is substantially level with the reciprocating platform  24 , to permit withdrawal of the wheelchair lift  22  into the stowage compartment. Finally, in the raised position, the lift platform  28  is displaced upwardly to position the lift platform  28  adjacent an entryway of the motor vehicle.  
         [0023]    Extending between the attachment arm assemblies  26   a  and  26   b  is a torsion tube  27 . The torsion tube  27  is welded on each end to the attachment arm assemblies  26   a  and  26   b.  As well known in the art, the torsion tube  27  actuates the lift platform  28  between the lowered position, intermediate position and the raised position by applying torque to the attachment arm assemblies  26   a  and  26   b.    
         [0024]    Each attachment arm assembly  26   a  and  26   b  includes a support arm  30   a  and  30   b  and a balance arm  32   a  and  32   b.  Each attachment arm assembly  26   a  and  26   b  is identical. Therefore, for clarity, only one attachment arm assembly shall be described in greater detail. However, it should be apparent that the description for one attachment arm assembly is applicable to the other assembly.  
         [0025]    One end of the support arm  30   a  and balance arm  32   a  is coupled to opposite sides of one end of the reciprocating platform  24  by a well known attachment pin assembly  40   a  and  40   b,  such as a trunnion or cantilevered pin. The other end of the support arm  30   a  and balance arm  32   a  is similarly fastened to opposite sides of the lift platform  28  by a well known support arm pin  42  and balance arm pin  44 . As coupled to both the reciprocating platform  24  and lift platform  28 , the attachment arm assemblies  26   a  and  26   b  permit hinged movement of the lift platform  28  relative to the reciprocating platform  24 .  
         [0026]    Referring now to FIGS. 1 and 3, the support assembly  20  will now be described in greater detail. Although a single support assembly  20  is illustrated as attached to each one of the attachment arm assemblies  26   a  and  26   b,  the invention is not intended to be so limited. As a non limiting example, two or more support assemblies may be attached to each attachment arm assembly  26   a  and  26   b.  Further, each support assembly  20  is identical and, therefore, only one support assembly will be described in greater detail. However, it should be apparent that the description for one support assembly  20  is applicable to the other.  
         [0027]    The support assembly  20  includes first and second plates  34   a  and  34   b  and a pair of support pins  36   a  and  36   b.  Each plate  34   a  and  34   b  is suitably a rectangular member formed from a high strength material, such as steel. The plates  34   a  and  34   b  are fastened to opposite sides of the support arm  30   a  and balance arm  32   a  by the strap pins  36   a  and  36   b.  As seen best by referring to FIG. 3, the first strap pin  36   a  extends through one end of the first plate  34   a,  through a correspondingly located bore  46  extending laterally through the balance arm  32   a,  and through the second plate  32   b.  The second strap pin  36   b  extends through the first plate  34   a,  through a bore  48  extending laterally through the support arm  30   a,  and through the second plate  34   b.  Thus, as attached, the support arm  30   a  and balance arm  32   a  are sandwiched between the first and second plates  34   a  and  34   b  of the support assembly  20 .  
         [0028]    In operation, the lift platform  28  is supported by the support arms  30   a  and  30   b.  As noted above, the connection between the lift platform  28  and the support arms  30   a  and  30   b  is achieved by the support arm pin  42 . The lift platform  28  is maintained in a substantially horizontal position throughout its range of motion by the connection between the balance arms  32   a  and  32   b  through the balance arm pin  44 . It should be apparent that the phrase “substantially horizontal position” includes the normal operating range of a wheelchair lift within the scope of this disclosure. Thus, such normal operating ranges are within the scope of all embodiments of the present invention.  
         [0029]    In the event of a failure of one of the balance arm pins  44 , the lift platform  28  is maintained level by the balance arm located on the opposite side of the lift platform  28 . Although the lift platform  28  may drop slightly from its originally supported position, the support assembly  20  maintains the lift platform  28  in a plane substantially parallel to its original horizontal plane. As an example, in the event of failure of the balance arm pin  44  connecting the balance arm  32   a  to the lift platform  28 , the other balance arm  32   b  maintains the level positioning of the lift platform  28 .  
         [0030]    In the event of a failure of one of the support arm pins  42 , the lift platform load is transferred to the balance arms  32   a  and  32   b  by the support assembly  20 . The first and second plates  34   a  and  34   b  of each support assembly  20  transfer loads associated with the support arm to the corresponding balance arm, while maintaining the level positioning of the lift platform  28 . Thus, each support assembly  20  acts as a load transfer device, whereby in the event of a failure of one of the load bearing support arm pins, the load associated with the support arm is transferred to the balance arm by one or more of the support assemblies.  
         [0031]    Referring now to FIGS. 4 and 5, a support assembly  120  formed in accordance with another embodiment of the present invention will now be described in greater detail. The support assembly  120  of the second embodiment is identical in materials and operation to the first embodiment described above with the following exception. The support assembly  120  includes a U-shape saddle strap  140  formed from a high strength material, such as steel. The saddle strap  140  extends from one side of the support arm  30   a  to the other side of the support arm  30   a  to cradle the balance arm  32   a  within the saddle strap  140 . The saddle strap  140  is fastened to the support arm  30   a  by a plurality of fasteners  142 , such as bolts, extending through opposite sides of the saddle strap  140  and the support arm  30   a.    
         [0032]    In operation, in the event that the support arm pin  42  fails, the load of the support arm  30   a  is transferred to the balance arm  32   a  by the saddle strap  140 . In the event support arm pin  42  fails, the support arm  30   a  or  30   b  is held in position by the torque tube  27 . Because the saddle strap  140  is fastened to the support arm  30   a,  the saddle strap  140  is also held in position. However, because of the failed support arm pin  42 , the lift platform  28  drops slightly until the balance arm  32   a  is received within the saddle strap  140 . As a result, load is transferred to the balance arm  32   a.    
         [0033]    Referring now to FIGS. 6 and 7, a support assembly  220  formed in accordance with yet another embodiment of the present invention will now be described in greater detail. The support assembly  220  is identical in materials and operation to the embodiments described above with the following exceptions. As seen best by referring to FIG. 6, the support assembly  220  includes a U-shaped retaining plate  222  extending between the support arm pin  42  and balance arm pin  44 . Although the retaining plate  222  is suitably U-shaped in configuration, other shapes, such as two plates pinned to the outboard and inboard facing sides of the support arm  30   a  and balance arm  32   a,  are also within the scope of the present invention.  
         [0034]    As seen best by referring to FIG. 7, the support arm pin  42  and balance arm pin  44  are seated within the support arm  30   a  and balance arm  32   a,  respectively, on bushing housings  224   a  and  224   b.  The retaining plate  222  extends around one end of the support arm  30   a  and balance arm  32   a  and is coupled to each arm by the pins  42  and  44 .  
         [0035]    During normal operation, the support arm  30   a  and balance arm  32   a  are attached to the lift platform  28  using the support arm pin  42  and balance arm pin  44 . The support arm pin  42  and balance arm pin  44  are held in place by retaining rings (not shown) located on both ends. In the event of a pin breakage or displacement, the retaining plate  222  holds one of either the support arm  30   a  or balance arm  32   a  in place. The outer surface of the bushing housing  224   a  or  224   b  is trapped in place by the inner surface of shaft housing  226   a  or  226   b,  thereby constraining the system in the event of a pin failure. Thus, the contact between the inner surface of the shaft housing and the outer surface of the bushing housing are redundant to the function normally provided by the support arm pin  42  or balance arm pin  44 .  
         [0036]    While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.  
         [0037]    Although each of the foregoing embodiments have been described, it should be apparent that variations of embodiments are also contemplated and, therefore, are within the scope of the present invention. As a non-limiting example, the support assembly may be attached to one of either the support arm or balance arm, both of the support and balance arms, and/or both ends of the support and balance arms.