Abstract:
An automatic door reciprocating system ( 20 ) is disclosed. The automatic reciprocating system is adapted for use with a wheelchair lift ( 152 ) designed to be stowed in a lower compartment of a vehicle ( 24 ). The vehicle includes a floor and a sliding door ( 22 ) where the sliding door is slidable between open and closed positions. The wheelchair lift includes a platform that is movable between an upper position, where the platform is substantially coplanar with the floor, and a lower position. The automatic door reciprocating system includes a reciprocating assembly ( 26 ) for automatically reciprocating the sliding door between the opened and closed positions.

Description:
PRIORITY CLAIM (RELATED APPLICATION)  
       [0001]    Priority is claimed under 35 U.S.C. §119(e) from U.S. Provisional Patent Application Ser. No. 60/176,229, filed Jan. 14, 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 an automatic drive assembly for a wheelchair lift passenger access door.  
         BACKGROUND OF THE INVENTION  
         [0003]    The Americans With Disabilities Act (ADA) requires the removal of physical obstacles to those who are physically challenged. Consequently, there has been more emphasis in providing access systems to a motor vehicle, such as a tour or inter-city bus. In a typical tour bus, the floor may be located approximately fifty-four inches above the pavement, while the underside of the bus may be approximately thirteen inches above the pavement. Similarly, the floor of a railway car may often times be many feet above the floor of an adjacent platform. Such distances require a lifting mechanism that cannot easily be contained within the space available around the stairwell of such a bus or railway car.  
           [0004]    A common manner of providing the physically challenged with access to a tour bus or railway car is a platform-type wheelchair lift of the type disclosed in U.S. Pat. No. 5,111,914, issued to Kempf, the disclosure of which is hereby expressly incorporated by reference. Platform-type wheelchair lifts may be stowed beneath a passenger access door dedicated to providing access into and out of a motor vehicle for the physically challenged. In currently available designs, the passenger access door is manually operated between an open and close position, and is tied to the operation of the platform lift. Although such lifts are highly effective and are a significant improvement over prior lift designs, it has been determined that an automatic mechanism for the access door is desirable for several reasons.  
           [0005]    First, with an automatic mechanism, the entire wheelchair platform assembly may be operated from a single convenient location. A related advantage of such a mechanism includes the operation of both the platform lift and the door from one single hand-held control unit. Finally, because the mechanism is automated, there is no manual operation involved and, therefore, such a unit is more operator friendly than current designs.  
           [0006]    In view of the foregoing, there is a need for an automatic mechanism for a wheelchair lift passenger access door.  
         SUMMARY OF THE INVENTION  
         [0007]    In accordance with certain embodiments of the present invention, an automatic door reciprocating system for use with a wheelchair lift is provided. The wheelchair lift is designed to be stowed within a lower compartment of a vehicle having a floor and a sliding door. The sliding door is slidable between open and closed positions. The wheelchair lift includes a platform that is movable between an upper position, where the platform is substantially coplanar with the floor, and a lower position. The automatic door reciprocating system includes a reciprocating assembly for automatically reciprocating the sliding door between the open and closed positions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    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:  
         [0009]    [0009]FIG. 1 is a perspective view of an automatic mechanism formed in accordance with one embodiment of the present invention for a wheelchair access door;  
         [0010]    [0010]FIG. 2 is a perspective view of a drive assembly of an automatic mechanism for a wheelchair lift passenger access door formed in accordance with one embodiment of the present invention;  
         [0011]    [0011]FIG. 3 is a perspective view of a plug shaft assembly for an automatic mechanism for a wheelchair lift passenger access door formed in accordance with one embodiment of the present invention;  
         [0012]    [0012]FIG. 4 is a perspective view of an automatic mechanism for a wheelchair lift passenger access door formed in accordance with one embodiment of the present invention, showing a plug drive assembly and a latch assembly;  
         [0013]    [0013]FIG. 5 is a planar view of the plug drive assembly and latch assembly of FIG. 4, showing the position of the plug drive assembly and latch assembly when the passenger access door is in a plugged position;  
         [0014]    [0014]FIG. 6 is a planar view of the plug drive assembly and latch assembly of FIG. 4, showing the plug drive assembly and latch assembly when the passenger access door is in an unplugged position;  
         [0015]    [0015]FIG. 7 is a perspective view of a manual release mechanism of an automatic mechanism for a wheelchair lift passenger access door formed in accordance with one embodiment of the present invention, showing the manual release mechanism in a release position;  
         [0016]    [0016]FIG. 8 is an environmental view of an automatic mechanism for a wheelchair lift passenger access door, showing the door in the plugged position and the platform lift located a predetermined distance from the passenger access door;  
         [0017]    [0017]FIG. 9 is an environmental view of an automatic mechanism for a wheelchair lift passenger access door formed in accordance with one embodiment of the present invention, showing the access door in an unplugged position;  
         [0018]    [0018]FIG. 10 is an environmental view of an automatic mechanism for a wheelchair lift passenger access door formed in accordance with one embodiment of the present invention, showing the access door in the fully open position with the platform lift extending partially into the vehicle;  
         [0019]    [0019]FIG. 11 is a logic diagram for operation of an automatic mechanism for a wheelchair lift passenger access door formed in accordance with one embodiment of the present invention, illustrating the logic to open the access door;  
         [0020]    [0020]FIG. 12 is a logic diagram for an automatic mechanism for a wheelchair lift passenger access door formed in accordance with one embodiment of the present invention, illustrating the logic to close the access door;  
         [0021]    [0021]FIG. 13 is an electrical circuit diagram of an automatic mechanism for a wheelchair lift passenger access door; and  
         [0022]    [0022]FIG. 14 is a planar view of a plug drive assembly and a latch assembly formed in accordance with an alternate embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    [0023]FIG. 1 illustrates an automatic door drive assembly  20  constructed in accordance with one embodiment of the present invention. The door drive assembly  20  is designed to be coupled within a passageway for a wheelchair access door  22  of a vehicle  24 , such as a tour bus or railway car. For ease of illustration, only a portion of the vehicle  24  is illustrated.  
         [0024]    The access door  22  is suitably a sliding door, mounted to the vehicle  24  by a front hanger  10  and a rear hanger  12  (FIG. 8). The front hanger  10  is mounted within a first track  14  located inside the vehicle  24 . Similarly, the rear hanger  12  is mounted in a second track  16  located on the outside of the vehicle  24 . The front hanger  10  is rigidly mounted to the access door  22 , on the inside of the access door  22  near the forward and top edges of the access door  22 . The rear hanger  12  is pivotally mounted to the access door  22 , on the outside of the access door  22  near the rear and top edges of the access door  22 . A door guide rail  18  is rigidly mounted on the inside face of the access door  22  and is arranged to guide the motion of the access door  22 , as is well known in the art.  
         [0025]    The door drive assembly  20  includes a drive assembly  26 , a plug shaft assembly  28 , a latch assembly  30 , a plug drive assembly  32 , and a belt assembly  34 . As seen best by referring to FIG. 2, the drive assembly  26  is suitably mounted near the top of the access door  22  by a main frame weldment  40 . The drive assembly  26  includes a driver assembly  42 , a driven idler assembly  44 , an overload switch assembly  46 , an idler assembly  48 , and a belt assembly  50 . The driver assembly includes a well known electric gear motor  60  coupled to a pulley (not shown). In turn, the pulley drives the belt assembly  50 .  
         [0026]    The belt assembly  50  includes a toothed timing belt  70  and upper and lower belt clamps  72  and  74  (FIG. 7). The upper and lower belt clamps  72  and  74  clamp the timing belt  70  and slide in a track  76 . The belt assembly  50  also includes a spring-loaded manual release dog  78  located at one end of the track  76 . As attached, the belt  70  moves in a circuit, such that the release dog  78  and front hanger  10  and door assembly  22  follow.  
         [0027]    The belt circuit is designed to provide a predetermined amount of belt tension when the access door  22  is actuated into the open direction. When the access door  22  is actuated in the closed direction, the tension in the belt assembly  50  is limited by a spring tension assembly  80 .  
         [0028]    The spring tension assembly  80  is coupled to the idler assembly  48  in a well known manner to limit the tension in the belt assembly  50  as the access door  22  is actuated into the closed position. As the access door  22  is actuated into the closed position and if the access door  22  is obstructed from moving in the closed direction, the tension in the belt  70  increases. As the tension in the belt  70  exceeds a pre-set amount and the idler assembly  48  is displaced downwards into switching contact with the overload switch assembly  46 , a signal is transmitted to the door controller (not shown), thereby indicating an overload condition.  
         [0029]    The overload switch assembly  46  includes a bias spring stop  46   b  and a switch mechanism  46   a,  such as a micro limit switch. The stop  46   b  is located near the overload switch assembly  46  and is adapted to limit travel of the idler assembly  48 , such that the belt  70  will not slip. Having received an overload signal, the door controller reverses the direction of access door  22  toward the full open position. Although the overload switch assembly  46  is preferably a micro-limit switch, other types of switches or sensors, such as a proximity sensor, are also within the scope of the present invention.  
         [0030]    Referring now to FIG. 3, the plugged shaft assembly  28  will now be described in greater detail. The plug shaft assembly  28  includes a shaft  90 , first and second arm weldments  92   a  and  92   b , a plug drive handle assembly  94 , and a plug drive plate assembly  96 . Preferably, the shaft  90  is hollow to allow electrical cables to pass from a location within the vehicle  24 , such as a baggage compartment, where the lift and door controllers are located, to the location of the drive assembly  26 . Although a hollow shaft  90  is preferred, other types of shafts, such as a solid shaft, are also within the scope of the present invention.  
         [0031]    Each arm weldment  92   a  and  92   b  includes a shaft arm  98   a  and  98   b  and a roller  100   a  and  100   b.  One end of the shaft arm  98   a  and  98   b  is fixed to the shafts  90 . One of the first and second rollers  100   a  and  100   b  is disposed at the other end of each shaft arm  98   a  and  98   b.  The rollers  100   a  and  100   b  roll in the guide door rails  18  located on the access door  22 .  
         [0032]    The plug drive handle assembly  94  is fixed to one end of the shaft  90  and includes a latch detent  110 , a bias spring  112 , and a manual operation handle  114 . The plug drive handle assembly  94  also includes a manual release dog  116 . The manual release dog  116  fits within a hole  114   a  located in the manual operation handle  114 . The dog  116  is of similar construction and operation as the dog  78 .  
         [0033]    Referring to FIG. 4, the plug drive plate assembly  96  is pivotally mounted on the shaft  90  and is connected to the manual operation handle  114  by the manual release dog  116 . The plug drive plate assembly  96  is also connected to the plug drive assembly  32 .  
         [0034]    Referring to FIGS. 4 and 5, the plug drive assembly  32  will now be described in greater detail. The plug drive assembly  32  includes a drive motor  120 , a master arm  122 , and a push rod assembly  124 . One end of the push rod assembly  124  is pinned to one end of the master arm  122 . The other end of the master arm  122  is similarly pinned to the drive motor  120 . The other end of the push rod assembly  124  is pinned to the plug drive plate assembly  96 .  
         [0035]    The drive motor  120  acts as a rotary actuator and transmits force through the push rod assembly  124  to drive the plug shaft assembly  28 . As noted above, the push rod assembly  124  is pinned to the plug drive plate assembly  96 . As a result, motion of the plug shaft assembly  28  is driven by actuation of the plug drive assembly  32 . The plug shaft assembly  28  travels through an angle of approximately 45 degrees when the door is actuated between a plugged and an unplugged position, as is described in greater detail below.  
         [0036]    Referring now to FIGS. 5 and 6, the latch plate assembly  30  will be described in greater detail. The latch plate assembly  30  includes a latch arm  130 , a solenoid  132 , a latch sensor  134 , a plugged sensor  136 , and an unplugged sensor  138 . The latch arm  130  extends between the solenoid  132  and the latch sensor  134 .  
         [0037]    The latch arm  130  includes a notch  142  sized to lockingly receive the latch detent  110  of the plug drive handle assembly  94 . The spring loaded latch arm  130  catches the latch detent  110  of the plug drive handle assembly  94 , thereby holding the access door  22  in a closed and locked position. In this position, the latch sensor  134  indicates that the latch arm  130  is in the latched position.  
         [0038]    As seen best by referring to FIG. 5, in the latched position, the free end of the manual operation handle  114  is displaced against the plugged sensor  136 , thereby indicating that the door assembly  22  is in the plugged position.  
         [0039]    As seen best by referring to FIG. 6, the latch plate assembly  30  may be selectively actuated into the unplugged position by the plug drive assembly  32 . In this position, the drive motor  120  pulls the push rod assembly  124  to rotate the manual operation handle  114  into a position relative to the unplugged sensor  138  indicative that the access door  22  is unplugged. In this position, the solenoid  132  releases the latch arm  130 , and the latch arm  130  is no longer in contact with the latch sensor  134 . After the latch arm  130  is released, the access door  22  may be unplugged. Although the current embodiment of the present invention describes the latch, plugged and unplugged as sensors, other devices, such as switches, are also within the scope of the present invention.  
         [0040]    It should be apparent that the access door  22  can be actuated by a variety of different methods, including electric, as described above, hydraulic, pneumatic, by motors or cylinders, and with or without belts. Further, a manual override is possible by releasing the manual release dog  78 . As best seen by referring to FIG. 7, the manual release dog  78  may be spring loaded and transmits a force from the upper and lower belt clamps  72  and  74  to the front hanger  10 . In the event of a power failure, the manual release dog  78  may be decoupled from the lower belt clamp  74  by pulling an “L” shape lever pin  150  downwardly within the manual release dog and rotating the lever pin  150 , such that the base portion of the pin  150  is selectively locked against the lower edge of the manual release dog  78 .  
         [0041]    When the lever pin  150  is displaced into the unlocked position, the other end of the lever pin  150  is removed from within the lower belt clamp  74 , thereby allowing the access door  22  to be manually plugged and unplugged, as well as reciprocated between the open and closed positions. Further, the door open and close driving motion, and/or the plugging and unplugging drive motion may be back driven in the event of power failure, without releasing the manual dog  78 . Also, during manual operation, a bias spring  212  urges the manual operation handle  114  toward either plugged or unplugged positions in a toggle like manner.  
         [0042]    Operation of the door drive assembly  20  may be best understood by referring to FIGS.  8 - 10 . To clarify operation of the current embodiment of the present invention, a well known platform lift  152 , such as that disclosed in U.S. Pat. No. 5,158,419, issued to Kempf et al., the disclosure of which is hereby expressly incorporated by reference, is illustrated. The ramp platform  152  may be reciprocated between stowed and deployed positions, such that it may be selectively positioned adjacent the access door  22  to load and unload passengers from the lift  152 .  
         [0043]    When approaching the access door  22  of a vehicle  24 , the lift  152  stops a predetermined distance of reaching the access door  22  and sends a signal to open the access door  22  to a well-known door controller  154 . The door controller  154  having received an open signal, unlatches the access door  22 . The access door  22  is unplugged, using the drive assembly  26  as described above.  
         [0044]    As seen best by referring to FIG. 9, one edge of the door assembly  22  is displaced outwardly away from the vehicle  24 . In this position, the unplugged sensor  138  indicates a door unplugged position to the door controller  154 . The access door  22  is then opened by the drive assembly  26 , as also described above. When the access door  22  is in the fully open position, a portion of the access door  22  comes into contact with a door open sensor  156  (FIG. 2), thereby indicating to the door controller  154  that the access door  22  is open. The door controller  154  then sends a signal to the lift controller (not shown) that the access door  22  is open. The lift  152  then proceeds to the vehicle floor and docks with the vehicle floor, as seen in FIG. 10.  
         [0045]    The door controller  154  works in reverse as described to close the access door  22 . To close the access door  22 , the lift  152  undocks from the vehicle floor and moves away from the door opening a predetermined distance and stops. The lift controller sends a signal to the door controller  154  to close the door. Using the drive assembly  26 , the door controller  154  closes the access door  22  until a close door sensor  158  (FIG. 2) indicates that the access door  22  is closed. The access door  22  is then plugged and latched using the drive assembly  26 , as described above. The door controller  154  then sends a signal that the access door  22  is latched. The lift controller then resumes control of the lift  152  to a lower or stowed position.  
         [0046]    Operation of the door drive assembly  20  may be further understood by referring to FIGS. 11 and 12. In FIG. 11, the platform of the lift  152  is assumed to be at the height of the floor for the vehicle  24  and the door controller  154  is actuated into the open door position. In this position, a single is sent to a door control circuit (DCC) from the lift control circuit. The DCC reads the closed door sensor  158  and determines whether the access door  22  is closed, as indicated by the decision block  170 . In the event that the DCC has an indication that all signals are high, typically recognized as positive voltage, the circuits will then actuate the drive motor  120  in connection with the solenoid  132  of the latch plate assembly  30 . The purpose of this dual action is to remove excess friction of the latch mechanism and allow for an easier unlatching action by the solenoid  132 , and generally indicated by the block  174 .  
         [0047]    The circuit then determines whether the latch arm  130  is in the unlatched position, as indicated by the decision block  178 . If the circuit indicates that the latch arm  130  is in an unlatched position, it then reverses power to the drive motor  120 , as indicated by the block  180 . This causes the access door  22  to pull away from its plugged and latched position.  
         [0048]    When the access door  22  has reached a full unplugged position (FIG. 9), the unplugged sensor  138  is actuated and gives the circuit a signal. The circuit verifies that the access door  22  is unplugged, as indicated by the decision block  182 . This signal, in conjunction with an unlatched indication and an open door signal, passes through a set of relay contacts and then to a field effect transistor (FET), commonly referred to as a source driver. This source driver actuates a high current relay which actuates the electric gear motor  60  in the open direction, as generally indicated by the block  184 . The use of the relay in this manner not only allows for a higher current source, but also allows the use of a separate voltage source and provides for isolation from the controlling circuit voltage. A further advantage of such a circuitry is to provide for a ground potential on both sides of the motor  60  to minimize arcing on activation of the relay contacts.  
         [0049]    When the access door  22  has reached a full open position, as generally indicated by the decision block  186 , the door open sensor  156  is activated and sends a signal to the DCC. This signal terminates the logic action that causes the motor  60  to operate in the open direction. At this point, the DCC also sends a signal to the lift control circuit that a raise function can now be continued, as generally indicated by the block  188 .  
         [0050]    With reference to FIG. 12, actuation of the access door  22  to the closed position will now be described in greater detail. For purposes of FIG. 12, the platform of the lift  152  is assumed to be undocked from the floor level of the vehicle  24  and the lift controller output indicates that the access door  22  is to be actuated into the closed position. In this position, a signal is sent to the DCC from the lift control circuitry. This signal, in conjunction with a not closed signal, generally indicated by the decision block  190 , and a signal that the access door  22  is unplugged, as generally indicated by the decision block  192 , will activate the electric motor  60  to the closed position, generally indicated by the block  194 . This causes the access door  22  to commence closing and move away from the door open switch  156 . The loss of the door open signal is conditioned by the logic in the DCC and is applied as a reset signal to the relay.  
         [0051]    During the close mode, if an obstacle should impede the closing motion, as generally indicated by the decision block  196 , the overload switch  46   a  is activated, thereby sending a signal to the DCC. This signal causes the relay to set. This set action redirects the close signal to cause the electric gear motor  60  to reverse direction to open, as generally indicated by the block  198 . If this action is allowed to continue, the access door  22  will reach a full open position, as generally indicated by the decision block  200 , and activate the door open switch  156 , which, in turn, sends a signal to the DCC which resets the relay and reverses the access door  22  direction to cause a closing action. If the obstruction is not removed, this action will repeat itself until the door closed command is terminated. The operator can, alternately, deselect “lower” from the lift controller. This action also resets the DCC after an obstruction has been detected. After the obstruction has been removed, and the “lift lower” is selected, the access door  22  will move towards the closed position.  
         [0052]    When the access door  22  reaches the closed position, the door close sensor  158  sends a signal to the DCC, as generally indicated by the decision block  202 . This signal, in conjunction with the close door command and the unplugged signal, will cause the drive motor  120  of the plug drive assembly  32  to actuate in the plug direction, as generally indicated by the block  204 . When the access door  22  reaches the plugged position, the latch sensor  134  sends a signal to the DCC that causes the signal to the drive motor  120  to be removed, as generally indicated by the decision block  206 . With the access door  22  in the plugged position, the latch mechanism causes this same signal to be sent to the lift control circuitry, as generally indicated by the block  208 , thereby allowing for normal lift operation to continue.  
         [0053]    An exemplary circuit used in the above embodiment of the door drive assembly is illustrated in FIG. 13.  
         [0054]    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. As a non-limiting and referring FIG. 14, the push rod assembly  124  may be driven over center to provide additional mechanical latching.