Abstract:
A wheelchair lift having a foldable platform including a first platform portion foldably coupled to a second platform portion, a lifting frame, at least one lifting arm with one end pivotally coupled to the lifting frame and the other end connected to the second platform portion and adapted to pivot the lifting arm between a substantially vertical stowed position and a substantially horizontal deployed position. A post extends from the lifting arm and a locking assembly is pivotably coupled to the lifting frame. The locking assembly includes a lever arm pivotably coupled to the lifting frame, a gas spring extending between the lever arm and the lifting frame which operates to resist pivoting of the lever arm, and a mechanical spring extending between the lever arm and the lifting frame which exerts a biasing force operating to pivot the lever arm to engage the post. Pivoting the lifting arm to the deployed position actuates unfolding the platform, while pivoting the lifting arm to the stowed position actuates folding the platform and engages the post with the lever arm.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. § 120 from U.S. Provisional Application Ser. No. 60/175,746, filed Jan. 12, 2000. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention generally relates to passenger or wheelchair lifts and, more particularly, to an apparatus for locking a wheelchair lift in the stowed position. 
     BACKGROUND OF THE INVENTION 
     As is known in the art, various types of lifting devices are used to move passengers between a lowered level, such as a ground level, and an elevated level, such as the floor level of a vehicle. For example, U.S. Pat. No. 5,445,488 to Saucier et al., the specification and drawings of which are hereby incorporated by reference herein in their entirety, illustrates therein a typical dual parallel arm hydraulic lift, which is reproduced herein as FIG.  1 . 
     The lift L includes a platform  12  that may be used to lift passengers, such as those in wheelchairs, from a ground level to a floor level F of the vehicle V by actuation of hydraulic cylinders  38 . When the platform  12  reaches the floor level F, a bridge plate  34 , which is pivotally coupled to the platform  12 , operates to bridge any gap between the platform  12  and the floor F, thereby allowing smooth transfer of the wheelchair between the platform  12  and an interior of the vehicle V. 
     When not in use, the platform  12  is folded to a vertical position (the stowed position) such that the entire lift L is disposed within the vehicle V, allowing the doorway D of the vehicle V to be closed. A known problem with such an arrangement is that the hydraulic cylinders  38  will typically drift over time, possibly allowing the platform  12  to come to rest against the inside of the vehicle door. Not only can this produce an annoying rattling during movement of the vehicle, but it can also impede operation of the door. 
     A solution to this problem is proposed in the &#39;488 patent by locking a protrusion on the bottom of the bridge plate  34  into a cavity  41  in the vehicle floor F. Interference between the bridge plate  34  (which is attached to the platform  12 ) and the cavity  41  prevents the stowed platform  12  from drifting outward. This solution is undesirable for a number of reasons, chief among them being the relatively large number of parts required to releasably latch the bridge plate  34 . 
     There is therefore a need for an apparatus that prevents drift of a stowed lift platform, without requiring a large number of parts or a complex interconnection of those parts. The present invention is directed toward meeting this need. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a wheelchair-lifting platform for transporting a passenger seated in a wheelchair back and forth between a passenger door of a vehicle and the ground, such that the platform can be automatically folded, retracted, secured and stored in the vehicle when not in use and that can be automatically released, unfolded and deployed when in use. One embodiment of the present invention is an automatically folding and unfolding platform having a spring-loaded and dampened latching hook that automatically latches the platform when it is retracted and automatically releases the platform at the start of its deployment cycle. The platform is folded and stored within the vehicle when not in use. 
     One object of the present invention is to provide an improved wheelchair-lifting platform. Related objects and advantages of the present invention will be apparent from the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a prior art wheelchair lift extending from a vehicle. 
     FIG. 2 is a partial perspective view of a first embodiment of the present invention, a wheelchair lift secured by a locking assembly. 
     FIG. 3 is a first enlarged partial perspective view of the embodiment of FIG.  2 . 
     FIG. 4 is a second enlarged partial perspective view of FIG.  2 . 
     FIG. 5 is a third enlarged partial perspective view of the locking assembly of FIG.  2 . 
     FIG. 6A is a schematic view of the platform assembly of the present invention in a folded and locked position. 
     FIG. 6B is a schematic view of the platform assembly of the present invention in a folded and unlocked position. 
     FIG. 6C is a schematic view of the platform assembly of the present invention in a partially deployed position. 
     FIG. 6D is a schematic view of the platform assembly of the present invention in a deployed position. 
     FIG. 7 is a partial perspective view of a second embodiment of the present invention. 
     FIG. 8 is a first enlarged partial perspective view of FIG. 7 showing a disengaged locking assembly. 
     FIG. 9 is an enlarged partial perspective view of FIG.  8 . 
     FIG. 10 is a second enlarged partial perspective view of FIG. 7 showing an engaged locking assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and alterations and modifications in the illustrated device, and further applications of the principles of the invention as illustrated therein are herein contemplated as would normally occur to one skilled in the art to which the invention relates. 
     FIGS. 2-6D illustrate a standard hydraulic parallel arm lift, indicated generally at  100 , to which a first embodiment locking device  115  of the present invention has been incorporated. The lift  100 , which is best viewed in its entirety in FIG. 6D, includes a lifting frame  102  attached to the entry doorway of the vehicle that is to be serviced by the lift  100 . The lift  100  further includes a foldable platform  104 , which is movable with respect to the frame  102  by some lifting means known in the art, such as a pair of parallel arms  106  driven by a hydraulically actuated cylinder  107 . In accordance with the present invention, a lever arm  108  is pivotally connected to the lifting frame  102  at pivot point  110 . Pivot point  110  located near the bottom of lifting frame  102  and is configured such that the lever arm  108  is relatively free to rotate therearound. The lever arm  108  is connected to pivot point  110  near its proximal end, the lever arm  108  having an opposite, distal end. A first biasing member  112 , such as a mechanical spring, is coupled between the lever arm  108  and the lifting frame  102  in such a way as to bias the lever arm  108  toward the platform  104 . The lever arm  108  is further coupled to the lifting frame  102  by means of a second biasing and/or motion-damping member  114 , such as a gas spring. The lever arm  108 , pivot point  110 , and the first and second biasing members  112 ,  114  together define a locking assembly  115 . 
     Gas spring  114  is coupled to the lifting frame  102  at a pivot point  116 . The lever arm  108  includes a notch  118  formed therein near its distal end. A post  120  is secured to the platform  104  such that the post  120  will be engaged within the notch  118  when the platform  104  is moved into the stowed position. In this embodiment, the post is secured to a biasing member  130  adapted urge the platform  104  into the stowed position, although the post  120  may be secured to any portion of the platform  104  convenient to the placement of the locking assembly  115 . The distal end of the lever arm  108  includes a curved camming surface  124  (see FIGS. 2-5) effective to guide the post  120  into the notch  118  when the platform  104  is stowed. A recess  132  is preferably formed into the lifting frame  102  to accommodate the locking assembly  115  during the platform  104  retraction, locking and/or unlocking operations. 
     The operation of the locking assembly  115  is illustrated schematically in FIGS. 6A-D. Prior to stowing the platform  104  (as can be best seen in FIG.  6 D), the spring  112  acts to pivot the lever arm  108  around the pivot point  110  so that it is in the position shown corresponding to approximately full extension of the gas spring  114 . As the platform  104  is folded into the stowed position, the post  120  comes into contact with the curved camming surface  124 . Further retraction of the platform  104  into the stowed position causes the lever arm  108  to pivot around the pivot point  110  in a direction which compresses the gas spring  114  and extends the spring  112  by virtue of the camming surface  124  sliding upon the post  120  (i.e., the pivoting force acts in a direction opposite the direction urged by the biasing member  112 ). Once the post  120  has cleared the camming surface  124 , it slips into the notch  118 . This corresponds to the fully stowed position of the platform  104  illustrated in FIG.  6 A. Because the lever arm  108  provides a secure connection between the lifting frame  102  and the platform  104 , any drift of the hydraulic lifting cylinders  107  will not result in outward movement of the platform  104 . The platform  104  is held securely in position by the physical interference of the lever arm  108 /notch  118  with the post  120 . 
     In order to unfold the platform  104  from the stowed position, the control system operating the hydraulic lifting cylinders  107  is programmed to momentarily further retract the hydraulic lifting cylinders  107  in the stowed direction.(see FIG. 6B) before reversing direction and unfolding the platform  104  away from the vehicle (see FIGS.  6 C- 6 D). This momentary movement in the stowed direction causes the post  120  to push the lever arm  108  further backwards, compressing the gas spring  114  and extending the spring  112 . In other words, moving the folded platform  104  further toward the stowed position before moving the platform  104  into the deployed position disengages the locking assembly  115  from post  120 . The hydraulic cylinders  107  are operated in this direction just long enough to move the lever arm  108  back far enough such that the post  120  may now clear the notch  118  when the platform  104  is deployed (i.e., folded away from the vehicle entrance). It will be noted that as soon as the hydraulic lifting cylinders  107  move the platform  104  away from the stowed position, the spring  112  will act to pivot the lever arm  108  back into locking position; however, momentary resistance offered by the gas spring  114  prevents the lever arm  108  from being pivoted into the locking position until the post  120  has cleared the notch  118 , thereby allowing the platform  104  to be unfolded from the stowed position. The force of the spring  112  does, however, eventually overcome the resistance of the gas spring  114 , thereby positioning the lever arm  108 /notch  118  into position for latching to the post  120  the next time the platform  104  is folded into the stowed position (i.e. the lever arm  108  is automatically reset). 
     Those having ordinary skill in the art will recognize that the lever arm  108  provides a simple and effective means for locking the platform  104  to the lifting frame  102  in order to prevent drift of the platform  108  when the lift is in the stowed position. Although only one side of the lift  100  is illustrated in FIGS. 2-6D, the preferred embodiment of the present invention includes a lever arm  108  positioned to couple the platform  104  on either side thereof, although the present invention contemplates the use of only a single lever arm  108 . Furthermore, an alternative embodiment allows integration of the spring  112  and the gas spring  114 , such that the gas spring  114  includes an internal spring, which tends to urge the gas spring  114  into its extended position. 
     As is known in the art, movement of the lift  100  is normally controlled by an automatic control system that moves the lift  100  in response to commands from a human operator. Such commands are normally given by activating one or more switches (not shown) coupled to the control system. From the above description, it will be recognized by those having skill in the art that the control system is desirably programmed to momentarily move the lift toward the stowed position when the operator commands deployment. This moves the lever arm  108  out of engagement with the post  120 . The control system may then move the lift  100  toward the deployed position in the normal manner. The present invention also comprehends the use of a control system that requires the operator to command movement toward the stowed position followed by a command for movement toward the deployed position (i.e., not an automated sequence) in order to disengage the locking assembly  115 . 
     Referring to FIGS. 7-10, there is shown a second hydraulic parallel arm lift, indicated generally at  100 A, to which a second embodiment locking device  115 A has been incorporated. The lift  100 A includes a lifting frame  102 A that is permanently or semi-permanently attached to the entry doorway of the vehicle that is to be serviced by the lift  100 A. The lift  100 A further includes a foldable platform  104 A, which is moved with respect to the frame  102 A by some lifting means  106 A known in the art, such as a pair of parallel lifting arms. Preferably, the lifting arms  106 A are actuated by one or more hydraulic cylinders  107 A. The platform  104 A is preferably hinged to accommodate folding, and is more preferably adapted to move between an extended, deployed orientation and a folded, stowed orientation. The lift  100 A is illustrated in the stowed orientation in FIG.  7 . In accordance with the present invention, a lever arm  108 A is pivotally connected to the lifting frame  102 A at pivot point  110 A. Pivot point  110 A is configured, such as by means of a bolt and nut, such that the lever arm  108 A is relatively free to rotate therearound. The lever arm  108 A is connected to pivot point  110 A near its proximal end, the lever arm  108 A having an opposite, distal end. A first biasing member  112 A, such as a mechanical spring, is coupled between the lever arm  108 A and the lifting frame  102 A in such a way as to bias the lever arm  108 A toward the platform  104 A. The lever arm  108 A is further coupled to the lifting frame  102 A by means of a second biasing and/or motion-damping member  114 A, such as a gas spring. The gas spring  114 A is coupled to the lifting frame  102 A at a pivot point  116 A. The lever arm  108 A, pivot points  110 A,  116 A and the first and second biasing members  112 A,  114 A together define a locking assembly  115 A. 
     The arrangement of the lever arm  108 A is shown in greater detail in FIGS. 8-10. The lever arm  108 A includes a notch  118 A formed therein near its distal end. A post  120 A is secured to a side rail  122 A of the platform  104 A such that the post  120 A will be engaged within the notch  118 A when the platform  104 A is moved into the stowed position shown in FIG.  7 . As can be seen in the views of FIGS. 8 and 9, the distal end of the lever arm  108 A includes a curved camming surface  124 A that is effective to guide the post  120 A into the notch  118 A when the platform  104 A is stowed. 
     It will be appreciated that the second embodiment locking assembly  115 A operates in substantially the same manner as the first embodiment locking assembly  115 , the substantial difference being the locations of the pivots  110 A/ 116 A with respect to the lifting frame  102 A and the location of the post  120 A with respect to the platform  104 A. It is thus illustrated that the relative location of the various components of the locking assembly of the present invention are not critical, all such arrangements falling within the scope of the present invention. 
     As described above, the post extends from the lifting arm/platform assembly and the locking assembly is coupled to the frame. It will be appreciated by one having ordinary skill in the art that the invention will also function with the post extending from the frame and the locking assembly connected to the lifting arm/platform assembly. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.