WO1997046199A1

WO1997046199A1 - Wheelchair lift with belt drive mechanism

Info

Publication number: WO1997046199A1
Application number: PCT/US1997/009854
Authority: WO
Inventors: Alan R. Cohn
Original assignee: Lift-U, Division Of Hogan Mfg., Inc.
Priority date: 1996-06-07
Filing date: 1997-06-04
Publication date: 1997-12-11
Also published as: AU3304397A

Abstract

A platform-type wheelchair lift for mounting in the stairwell of a vehicle, such as a bus or train. The wheelchair lift includes a platform frame that is movable from a retracted position in which it is stowed underneath the vehicle to an extended position in which it extends out from the side or back of the vehicle. The platform frame is moved between the extended and retracted positions by a belt drive mechanism. A wheelchair platform is movably coupled to the platform frame by a parallelogram linkage that allows the wheelchair platform to move between a lowered and a raised position. The wheelchair platform includes foldable outer and inner wheelchair barriers that prevent a wheelchair from moving off of the wheelchair platform during operation of the wheelchair lift.

Description

WHEELCHAIR LEFT WITH BELT DRIVE MECHANISM

Field of the Invention The present invention relates to wheelchair lifts, and more particularly, to platform type wheelchair lifts that include platforms that extend out from the side or back of a vehicle and move between a lowered position and a raised position

Background of the Invention

Wheelchair lifts of the type installed in the stairwells of transit vehicles, such as city buses, are well-known One type of wheelchair lift commonly referred to as a

"step lift," is illustrated in U S Patent No 4,466,771 to Thorley et al (the '771 patent) Another type of wheelchair lift, commonly referred to as a "platform lift," is illustrated in U S Patent No 4,058,228 to Hall (the '228 patent)

Both wheelchair step lifts and platform lifts typically include a wheelchair platform that is movable from a lowered position in which the wheelchair platform lies adjacent the sidewalk or ground to a raised position in which the wheelchair platform lies in the same plane as the aisle way of the bus, train, or other vehicle on which the lift is mounted A wheelchair is loaded onto the wheelchair platform when it is in the lowered or raised position at which time the platform is moved to the opposite position in order to allow the wheelchair to be moved into or out of the bus or other vehicle on which the wheelchair lift is mounted In order to decrease storage space and improve usability, a number of platform-type wheelchair lifts such as that described in the '228 patent include wheelchair platforms that retract under the bottom of the bus or other vehicle on which the lift is mounted In some wheelchair lifts such as that disclosed in the '228 patent the wheelchair platform forms the lower step of the vehicle entryway. Generally, wheelchair platforms have been extended and retracted through the use of either complex chain drive systems such as that disclosed in the '228 patent or through the use of a hydraulic actuation system such as that disclosed in U.S. Patent No. 4,134,504 to Salas et al. Both such extension and retraction systems are prone to problems. Chain drive systems tend to be complex, heavy, bulky, and require a great deal of maintenance including frequent adjustment and lubrication. Hydraulic drive systems are less prone to maintenance problems but generally require complex hydraulic control systems that are heavy, bulky, and expensive. In addition, neither the current chain drive nor hydraulic retraction and extension systems are easily disconnected to allow manual extension or retraction of the wheelchair lift in case of system failure.

Extension and retraction systems that use hydraulic drives also place a heavy load on the vehicle's electrical system. Similarly, wheelchair lifts that use chain drive systems generally use hydraulically driven motors and, thus also place a heavy load on the vehicle's electrical system. If the electrical load required by either the chain drive system or the hydraulic system could be reduced, it may be possible to use less capable electrical systems on the buses or other vehicles on which the wheelchair lifts are installed. In addition, it may be possible to install such wheelchair lifts on vehicles which could not otherwise accommodate the heavy electrical load placed on the vehicle by installing a wheelchair lift.

As can be seen from the above discussion, there exists a need for wheelchair lifts with improved extension and retraction mechanisms. The present invention is directed toward fulfilling this need.

Summary of the Invention One embodiment of the present invention is a wheelchair lift that includes a platform frame that is movable between an extended position in which it extends out from the side, front or back of the vehicle and a retracted position in which it may form the bottom step in the vehicle entryway. A wheelchair platform is coupled to the frame and is movable between a raised position in which a wheelchair may move from the interior of the vehicle onto or off of the wheelchair platform and a lowered position in which the wheelchair may be moved from the wheelchair platform onto the surface of the ground or vice versa. The wheelchair lift includes a belt drive mechanism that extends and retracts the platform frame and an actuation mechanism to raise and lower the wheelchair platform. According to other aspects of the invention, the belt drive mechanism includes a primary belt that is releasably fastened to a statutory frame of the wheelchair lift in order to allow the belt to be quickly disconnected. The belt is attached to the stationary frame at its opposing ends.

In accordance with other aspects in the invention, the belt drive mechanism includes at least one idler pulley and one drive pulley. The idler pulley and drive pulley are rotatably attached to the platform frame. The drive pulley is attached to a drive motor that is also coupled to the platform frame. The drive motor may be either an electric or a hydraulic motor.

In other embodiments in the invention, the belt drive mechanism includes two idler pulleys and a drive pulley, the drive pulley is mounted in-between the two idler pulleys. The belt passes over the idler pulleys and the drive pulley so that rotation of the drive pulley causes the platform frame to move along the belt. The drive mechanism can also include a secondary belt that passes over the drive pulley and a larger drive pulley in order to serve as a gear reduction mechanism on the drive motor. The wheelchair lift of the invention helps to reduce or eliminate a number of the disadvantages with prior art wheelchair lifts. The use of a belt drive mechanism to extend or retract the wheelchair platform simplifies the construction list and does not pose the complex maintenance, repair, and replacement problems prevalent in prior art wheelchair lifts. In addition, the belt drive mechanism uses a quick release primary belt that allows the belt drive mechanism to be quickly disconnected from the wheelchair lift frame. This in turn allows the platform frame to be manually extended or retracted in the case of a system failure.

In some embodiments, the use of a belt drive mechanism could also reduce the electrical power requirements of the wheelchair lift and thus, a vehicle in which the wheelchair lift is installed. In some applications the belt drive mechanism can use an electric motor to drive the belt drive mechanism. The use of an electric motor can reduce the electrical load placed on the vehicle's electrical system as compared to similar wheelchair lifts that use hydraulic chain drives or hydraulic motor belt drives.

Brief Description of the Drawings The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a perspective view of a wheelchair lift according to the present invention mounted within the entryway of a bus; FIGURE 2 is a perspective view of a wheelchair lift of the present invention showing the wheelchair platform retracted within the stationary frame of the wheelchair lift;

FIGURE 3 is a perspective view of the wheelchair lift of FIGURE 2 showing the wheelchair platform in an extended and a lowered position;

FIGURE 4 is a side elevational view of the wheelchair lift of FIGURE 2 illustrating the wheelchair platform in a lowered and a raised position;

FIGURE 5 is an enlarged, partial cutaway view of the attachment between the stationary frame and the slidable wheelchair platform frame; FIGURE 6 is an enlarged, partial cutaway view of the belt drive mechanism of the wheelchair lift of FIGURE 2;

FIGURE 7 is a partial side elevation view of the mounting plate and drive pulley;

FIGURE 8 is a side view of a second embodiment of the belt drive mechanism;

FIGURE 9 is a side view of a third embodiment of the belt drive mechanism.

Detailed Description of the Preferred Embodiment

A platform-type wheelchair lift generally designated 20 constructed according to the present invention is illustrated in FIGURES 1-3. The wheelchair lift 20 includes a generally rectangular stationary frame 22 that is mounted to the underside of a vehicle such as a bus or train. A wheelchair platform frame generally designated 24 is slidably mounted within the stationary frame 22 so that the platform frame may move between a first or retracted position (FIGURE 2) in which the platform frame is retracted underneath the floor of the vehicle to a second or extended position (FIGURE 3) in which the platform frame 24 extends outward from the vehicle on which the wheelchair lift is mounted. A wheelchair platform 26 is mounted within the platform frame 24 through the use of outer platform arms 28 and inner platform arms 30 so that the wheelchair platform may be moved from a lowered position as best seen in phantom in FIGURES 3 and 4 to a raised position as shown in FIGURE 4.

When the platform frame 24 is fully extended and the wheelchair platform 26 is in the lowered position (shown in phantom in FIGURES 3 and 4), a wheelchair occupant may maneuver a wheelchair onto or off of the wheelchair platform 26. The wheelchair platform 26 is then moved to its raised position (FIGURE 4), at which time the wheelchair occupant may maneuver the wheelchair into or out of the interior of the bus or other vehicle, as described in more detail below. The platform frame 24 is moved between the extended and retracted positions by a belt drive mechanism designated 32 (FIGURES 2 and 3). The belt drive mechanism 32 is attached to the platform frame 24 between outer and inner cross members 34 and 36 that extend across the width of the platform frame The belt drive mechanism 32 extends and retracts the platform frame 24 by moving the platform frame along a primary belt 38 that extends between an outer cross member 40 and an inner cross member 42 of the stationary frame 22 as best illustrated in FIGURES 2 and 3 and as described in more detail below

The wheelchair platform 26 is raised and lowered through the use of the outer and inner arms 28 and 30 The arms 28 and 30 are attached at one end to the wheelchair platform 26 and at the other end to two platform frame arms 44 that form the opposing sides of the platform frame 24 The outer and inner arms 28 and 30 are rotated around pivots on the platform frame arms 44 through the use of opposing pairs of parallel drive links 46 Each drive link 46 (FIGURE 4) is pivotably attached to an elongated end of the inner arms 28 and 30 (as best seen in FIGURE 4) as described in more detail below As the drive links 46 are moved outward or inward with respect to the platform frame arms 44, they cause the outer and inner arms 28 and 30 to rotate with respect to the platform frame arms Each drive link 46 and thus outer and inner arm 28 and 30 is driven by hydraulic actuator 48 Each hydraulic actuator 48 is attached at the actuator end to the inner end of the platform frame arms 44 and at the rod end to the inner end of the drive links 46 as best illustrated in FIGURE 2 and as described in more detail below

The wheelchair platform 26 includes a foldable outer wheelchair barrier 50 (FIGURE 2) and a foldable inner wheelchair barrier and wheelchair platform extension 52, (FIGURE 6) The outer and inner barriers 50 and 52 help to ensure that a wheelchair and wheelchair occupant remain on the wheelchair platform 26 during operation of the wheelchair lift 20 The structure and operation of the wheelchair platform and the foldable barriers will be described in more detail below

The rectangular stationary frame 22 includes two opposing side members 56 (FIGURE 2) that are separated by and joined together by the outer cross member 40, a middle cross member 58, and the inner cross member 42 The three cross members 40, 58, and 42 are located above the frame side members 56 and are joined to the frame side members at each end by angle pieces 60 that are welded or otherwise fastened to the frame side members 56 and the cross members 40, 58, and 42 The angle pieces 60 also serve as mounting brackets to attach the stationary frame 22 to the underside of a vehicle or other structure by bolting, welding, or other suitable fastening method.

Each frame side member 56 includes upper and lower inwardly extending elongated rails 62 and 64 as best illustrated in FIGURE 5. The platform frame 24 is slidably mounted within the stationary frame 22 through the use of a series of slide bearings 65 (FIGURE 5) mounted along the length of the platform frame arms 44. Each slide bearing 65 extends outward from the outer surface of the respective platform frame arm 44 into a slot formed by the upper and lower rails 62 and 64. It is advantageous to form the upper and lower rails 62 and 64 of wear resistant stainless steel or other material which does not corrode or pit and the slide bearings 65 out of a low friction material such as nylon, teflon, or another suitable low friction bearing material.

The platform frame 24 is formed of the opposing side platform frame arms 44 that are joined together by the outer cross member 34 (FIGURE 3) and the inner cross member 36. The inner cross member 36 is located approximately adjacent to the inner end of the platform frame arms 44 while the outer cross member 34 extends between a midpoint of the platform frame arms. The cross members 34 and 36 are attached to the platform arms 44 by welding, bolting, or other suitable fastening method. As described briefly above, the platform frame 24 is moved between its extended and retracted positions as shown in FIGURES 2 and 3 by the belt drive mechanism 32.

The belt drive mechanism 32 (FIGURES 2, 3 and 6) includes two opposing parallel support plates 66 that are spaced apart and joined at opposite ends to the outer cross member 34 and inner cross member 36 by welding, bolting, or other suitable fastening method. A drive motor 68 is mounted on one of the plates 66 such that the shaft of the drive motor extends through one of the plates 66 (FIGURE 6). A drive pulley 69 is mounted on the drive shaft between the two plates 66. The shaft end of the drive motor 68 is mounted to the plate 66 through the use of an oblong mounting plate 67 (FIGURES 6 and 7). The mounting plate 67 is welded, bolted or otherwise fastened to the drive motor 68. The lower end of the mounting plate 67 is pivotally bolted to the plate 66 through the use of a bolt 71 (FIGURE 7) that extends through the bottom portion of the mounting plate 67 and is received in the plate 66. The top of the mounting plate 67 is attached to the plate 66 through the use of a bolt 96 (FIGURES 6 and 7) that extends through a slot 97 in the upper portion of the mounting plate 67 and is received in a corresponding receptacle in the plate 66. The drive motor 68 and mounting plate 67 may be moved outward or inward as shown by arrow 94 (FIGURES 6 and 7) by rotating the mounting plate 67 and drive motor 68 around the lower pivotal mounting of the mounting plate 67 so that the bolt 96 slides within the slot 97. Moving the drive motor 68 outward or inward adjusts the tension of a drive reduction belt 76 that extends around the drive pulley 69 as described in more detail below.

Three axles including a drive axle 70 (FIGURE 6), an outer idler axle 72, and an inner idler axle 74 extend between the opposing plates 66. The drive reduction belt 76 extends around the drive pulley 69 and around a larger secondary pulley 78. The secondary pulley 78 is rotatably mounted on the drive axle 70 and is rigidly connected to a smaller secondary drive pulley 80 that is also rotatably mounted on the drive axle 70. The secondary pulley 78 serves as a reduction pulley to decrease the speed and increase the torque from the drive motor 68.

The primary belt 38 (FIGURE 6) extends over an inner idler pulley 82 that is rotatably mounted on the inner idler axle 74, underneath the secondary drive pulley 80 and over an outer idler pulley 84 that is rotatably mounted on the outer idler axle 72. The inner end of the primary belt 38 is attached to the lower surface of the inner cross member 42 by a quick release clamp 86 (FIGURES 3 and 6) that is bolted or otherwise releasably attached to the rear cross member 42 of the stationary frame 22. In the embodiment shown, the clamp 86 is attached using fasteners such as bolts (not shown) that extend through holes 88 in the clamp 86 and are received in corresponding holes (not shown) in the rear cross member 42. The outer end of the primary belt 38 is similarly attached to the outer cross member 40 of the stationary frame 22 by a quick release clamp 90 in a manner similar to the clamp 86.

As illustrated in FIGURE 6, the outer end of the primary belt 38 is attached to an adjustment lug 93. The adjustment lug 93 slides within a slot in the quick release clamp 90. The adjustment lug 93 may be slid inward or outward in order to loosen and tighten respectively the tension on the primary belt 38. After the tension of the primary belt 38 is adjusted, the adjustment lug 93 and thus primary belt 38 is locked in place by tightening a series of fasteners that extend through the holes 92 in the quick release clamp 90 and are received in the cross member 40 in holes (not shown).

As the shaft of the drive motor 68 and thus drive pulley 69 rotates counterclockwise as shown by arrow 94 (FIGURE 6), the large secondary pulley 78 and secondary drive pulley 80 rotate counterclockwise. The counterclockwise movement of the secondary drive pulley 80 causes the belt drive 32 and thus platform frame 24 to move outward along the length of the primary belt 38, thus extending the platform frame. Similarly, as the shaft of the drive motor 68 is rotated clockwise the platform frame 24 moves inward along the length of the primary belt 38, thus retracting the platform frame. The movement of the drive motor 68 and thus platform frame 24 is controlled by a control system (not shown) that is connected to the drive motor 68. The drive motor 68 could be either a hydraulic or an electrical motor to allow the primary belt 38 to be adjusted. In addition, the primary belt 38 can also be easily detached by loosening the clamps 86 and 90 to allow the platform frame to be disconnected from the stationary frame 22.

In alternate embodiments, instead of using fixed idler axles 72 and 74 and drive axle 70 and rotating pulleys 80, 82 and 84, rotating axles and fixed pulleys could be used. For example, the larger secondary pulley 78, secondary drive pulley 80, and idler pulleys 82 and 84 can be keyed to their respective shafts and the shafts could be allowed to rotate with bearings located in the mounting plates 66. In yet other embodiments, either the outer or inner idler pulleys 82 or 84 and the larger secondary pulley 78 could be eliminated. In still other embodiments, multiple belt drive mechanisms 32 could be used. For example, a separate belt drive mechanism 32 can be located on both sides of the platform frame 24.

For example, FIGURE 9 illustrates another embodiment of the belt drive mechanism 32. In the embodiment of FIGURE 9, a single outer idler axle 72 and outer idler pulley 84 are used in combination with a drive pulley 80 mounted on a drive axle 70. In this embodiment, the drive pulley 80 is either directly driven by a hydraulic or electric drive motor 68 or the drive motor 68 could be attached to a gear or other type of reduction mechanism that is attached to the drive axle 70 or drive pulley 80. The primary belt 38 passes over the top of the outer idler pulley 84 and then passes underneath the drive pulley 80. Although the embodiment illustrated in FIGURE 9 simplifies the mechanics of the belt drive mechanism 32, it is not preferred due to the increased bearing loads produced in the configuration.

Yet another embodiment of the belt drive mechanism 32 is illustrated in FIGURE 8. In the embodiment in FIGURE 8, the larger secondary pulley 78 is eliminated from the first embodiment illustrated in FIGURE and the drive pulley 80 is directly driven by the drive motor 68. Alternatively, as discussed above, the drive motor 68 could include a gear or other type of reduction mechanism that subsequently drives the drive pulley 80. The embodiment illustrated in FIGURE 8 is preferred over the embodiments of FIGURES 6 and 9 in some applications. The use of the duel idler pulleys 82 and 84 reduces bearing loads over the embodiment of FIGURE 9 and only increases complexity slightly. In addition, the use of a drive motor 68 that directly drives the drive pulley 80 or drives the drive pulley through a gear box eliminates the use of the drive reduction belt 76 and larger pulley 78 of the embodiment of FIGURE 6, thus possibly reducing system maintenance.

In any of the embodiments, the drive motor 68 could be either an electrical or a hydraulic drive motor that either incorporates a reduction mechanism or is attached to a separate reduction mechanism. The use of an electrical drive motor as opposed to a hydraulic drive motor is preferred in some applications because it can reduce the electrical load placed on the vehicle by the wheelchair lift.

The present invention's use of a belt drive mechanism 32 reduces the complexity and maintenance problems present in prior art hydraulic and chain drive systems used on wheelchair lifts. The belt drive system 32 also allows an operator to quickly loosen the fasteners attaching the clamps 86 or 90 to the stationary frame 22. Disconnecting the belt drive system 32 from the stationary frame 22 allows an operator to manually move the platform frame 24 between its extended and retracted positions in the case of a failure or malfunction of the wheelchair lift 20. As discussed briefly above, the wheelchair platform 26 is attached to the platform frame arms 44 by outer arms 28 and inner arms 30 that form a parallelogram linkage between the platform frame arms and the wheelchair platform. The parallelogram linkage keeps the platform frame arms 44 and wheelchair platform 26 parallel throughout the movement of the wheelchair platform from a lowered position to a raised position and vice versa. The ends of the arms 28 and 30 attached to the platform frame arms 44 are elongated (FIGURES 3 and 4) and include laterally spaced apart pivots that are attached to the platform frame arms 44 and the drive links 46. As best seen in FIGURE 4, the lower portion of the elongated portion of the arms 28 and 30 is pivotally attached to the platform frame arms 44 at pivots 100 and 102, respectively. The upper portion of the elongate portion of each arm 28 and 30 is attached to a drive link 46 at pivots 104 and 106, respectively. As the drive links 46 are moved outward or inward with respect to the platform arms 44 as best seen in FIGURE 4, the outer and inner arms 28 and 30 pivot about pivots 100 and 102, respectively, thus lowering or raising the platform 26. The inner end of each drive link 46 is attached to the rod of one of the hydraulic actuators 48 at a pivot 108 as best seen in FIGURES 2 and 3. The inner arms 30 are also joined together at the pivot points 102 by a torque tube 110 that is welded or otherwise fastened to the inner surfaces of the inner arms 30. The torque tube 110 ensures that the inner arms 30 move in unison and thus maintain the same orientation with respect to each other. The torque tube 1 10 allows the two hydraulic actuators 48 to work together and also ensures that if there is a malfunction in the wheelchair lift, the platform 26 is maintained at the same elevation on both sides and does not cant or lean, possibly causing harm to the wheelchair occupant.

The drive links 46 are moved outward or inward with respect to the platform frame arms 44 by the extension or retraction of the rods of the hydraulic actuators 48.

The hydraulic actuators 48 are attached to the drive links 46 at pivots 108 at one end and are pivotally attached to the platform frame arms 44 at pivot points 112 at the other end as best seen in FIGURE 3

In order to assist the platform 26 in clearing the stairs 124 (FIGURES 1-3) of the bus or similar vehicle on which the wheelchair lift 20 is mounted, the ends 120 and 122 of the arms 28 and 30, respectively, are bent upward or inward as shown in FIGURE 4 Configuring the wheelchair lift as shown with arms 28 and 30 having elongated portions attached at the upper end to a drive link 46 and at the lower end to a platform frame arm 44 and inwardly bent ends 120 and 122 helps the wheelchair platform 26 to clear the stairs 124 (FIGURE 4) without requiring an excessive extension of the platform frame 24 out from underneath the stairs 124

In alternate embodiments, the positions of the platform frame arms 44 and drive links 46 could be reversed such that the platform frame arms 44 attach to the upper end of the elongated portions of the arms 28 and 30 while the drive links 46 attach to the lower ends of the elongated portions Similarly, the configuration of the arms 28 and 30 could be reversed such that the elongated portion of the arms extended downward as opposed to upward in the preferred embodiment. The actuators 48 then push drive links 46 to raise the platform instead of pulling drive links 46 As best seen in FIGURE 4, outer and inner wheelchair barriers 50 and 52 are rotatably attached to the front edge of the wheelchair platform 26 and the rear edge of the wheelchair platform respectively The rear edge of the outer barrier 50 is rotatably attached to the front edge of the wheelchair platform 26 over its length by hinge 146 (FIGURE 3) The outer barrier rotates about the hinge 146 such that it is movable from a fully folded position as illustrated in FIGURE 3, to a fully extended position as illustrated in phantom in FIGURE 4 The inner barrier 52 (FIGURES 3 and 4) is rotatably mounted to the inner edge of the platform 26 using a hinge 184. The inner barrier 52 is movable between a fully retracted position in which the upper surface 186 of the inner barrier lies adjacent to the upper surface of the wheelchair platform 26 as illustrated as phantom position 256 in FIGURE 4, to an upright position illustrated as phantom position 188, and to a fully extended position in which -l i¬

the upper surface 186 forms an extension of the upper surface of the wheelchair platform 26.

The general operation of the wheelchair lift 20 will now be described. During standard operation of the bus or other vehicle on which the wheelchair lift 20 is mounted, the wheelchair lift 20 is maintained in its stowed position, as illustrated in FIGURE 2, underneath the bus. When the vehicle stops in order to load a wheelchair onto the vehicle, the wheelchair lift 20 moves as follows. First, the platform frame 24 is moved to an extended position by the belt drive mechanism 32. Once extended, the outer and inner barriers 50 and 52 are moved to upright barrier positions (FIGURE 4) by hydraulic actuators (not shown). The platform 26 is then lowered into contact with the ground by arms 28 and 30 actuated by drive links 46 which are actuated by hydraulic actuators 48. As the outer edge of a wheelchair platform 26 nears the sidewalk, wheels 258 (FIGURE 4) located at the front edge of the wheelchair platform contact the ground and allow the wheelchair platform to move in and out on the ground slightly as the vehicle tilts or rolls due to vehicle suspension movement during operation of the wheelchair lift. Once the wheelchair platform 26 contacts the ground, the control system (not shown) stops the downward movement of the wheelchair platform 26. The outer barrier 50 is then moved to an extended position as illustrated in phantom FIGURE 4. Once the wheelchair lift is fully deployed, a wheelchair occupant moves their wheelchair up the ramp formed by the outer barrier 50 onto the wheelchair platform 26. After the wheelchair is on the wheelchair platform, the outer barrier 50 moves to its upright barrier position 180, as shown in FIGURE 4. The wheelchair platform 26 is then raised to a raised position, as shown in FIGURE 4, by the arms 28 and 30 and drive links 46 and hydraulic actuators 48. Once the upper surface of the wheelchair platform 26 lies in the same plane as the upper surface of the stairs 124b (FIGURE 4), the inner barrier 52 moves to an extended position such that the inner barrier bridges the gap between the wheelchair platform 26 and the stairs 124b, as illustrated in FIGURE 4. The wheelchair occupant may then move his wheelchair into the interior of the bus or other vehicle over the inner barrier 52. In order for a wheelchair to be lowered from the interior of the bus to the sidewalk, the wheelchair lift operates in reverse order. After loading or unloading a wheelchair, the wheelchair platform 26, barriers 50 and 52, and platform frame 24, move to their fully retracted and stowed position, as illustrated in FIGURE 2. In addition to the foldable barriers 50 and 52, the wheelchair platform 26 also includes opposing hand rails 250 (FIGURE 2) that extend upward from the opposing edges of the wheelchair platform. The hand rails 250 may be placed within one of multiple recesses 252 located on the side of the wheelchair platform 26. The multiple recesses 252 allow the position of the hand rails 250 to be adjusted. This adjustment allows the wheelchair lift 20 to be used in different vehicles while still allowing the hand rails 250 to be positioned so that they do not interfere with the steps or doors of the vehicle. The hand rails 250 are secured within the recesses 252 by pins that extend through the hand rails 252 and holes 260 (FIGURE 4) in the walls of the recesses. The hand rails 250 could also be secured within the recesses by other suitable fastening methods. The wheelchair lift of the present invention reduces or eliminates a number of the problems associated with prior wheelchair lifts. The use of a platform frame 24 that slidably extends or retracts through the use of a belt drive mechanism 32 results in a number of advantages. The belt drive mechanism 32 is fairly simple and does not pose the complex maintenance, repair, and replacement problems prevalent in prior art wheelchair lifts. In addition, use of a quick release primary belt 38 allows the belt drive mechanism to be quickly disconnected, thus allowing the platform frame to be manually extended or retracted in the case of a system failure.

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.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A wheelchair lift comprising:

(a) a platform frame movable between an extended position and a retracted position;

(b) a wheelchair platform pivotally coupled to the platform frame, the wheelchair platform being movable between a raised position and a lowered position;

(c) a belt drive extension and retraction mechanism coupled to the platform frame to move the platform frame between the extended and retracted positions; and

(d) an actuation mechanism coupled to the platform frame and the wheelchair platform to move the wheelchair platform between the raised and lowered positions.

2. The wheelchair lift of Claim 1 , further comprising a stationary frame, in which the platform frame is movable mounted and wherein the belt drive extension and retraction mechanism is connected between the stationary frame and the platform frame so that operation of the belt drive extension and retraction mechanism moves the platform frame with respect to the stationary frame.

3. The wheelchair lift of Claim 1 , further comprising a stationary frame that is adapted to be attached to a vehicle, the platform frame being movably mounted within the stationary frame and the belt drive extension and retraction mechanism including a belt that is attached to the stationary frame at both ends

4. The wheelchair lift of Claim 3, wherein the belt drive extension and retraction mechanism further includes at least one pulley that is rotatably coupled to the platform frame and wherein the belt passes over said pulley.

5. The wheelchair lift of Claim 4, wherein the belt drive extension and retraction mechanism includes at least one drive pulley and one idler pulley, the drive pulley being coupled to a drive motor.

6. The wheelchair lift of Claim 5, wherein the drive motor is an electric motor.

7. The wheelchair lift of Claim 5, wherein the drive motor is a hydraulic motor.

8. The wheelchair lift of Claim 1, wherein the belt drive extension and retraction mechanism includes two idler pulleys that are parallel to each other and spaced apart so that they are rotatably coupled to the platform frame and a drive pulley rotatably coupled to the platform frame between the two idler pulleys, the drive belt extending at least partially around the idler pulleys and the drive pulley.

9. The wheelchair lift of Claim 3, wherein the belt is releasably attached to the stationary frame at both ends

10 The wheelchair lift of Claim 1 , further comprising a stationary frame in which the platform frame is mounted and wherein the belt drive extension and retraction mechanism includes a primary belt that is attached to the stationary frame at both ends, a drive pulley that is attached to a motor that is coupled to the platform frame, a secondary pulley that is larger than the drive pulley and is rotatably coupled to the platform frame and a secondary belt that passes over the drive pulley and the secondary drive pulley, and wherein the secondary drive pulley is rotatably coupled to the drive belt so that rotation of the secondary drive belt moves the platform frame between the extended position and the retracted position

11. A belt drive extension and retraction mechanism for use in a wheelchair lift having a platform frame that is movable between extended and retracted positions to move the platform frame between the extended and retracted positions, the belt drive mechanism comprising

(a) a belt that is connected at opposite ends to a stationary frame in which the platform frame is movably mounted,

(b) at least one idler pulley rotatably coupled to the platform frame;

(c) at least one drive pulley rotatably coupled to the platform frame and to a drive motor, and wherein the belt passes at least partially around the idler pulley and drive pulley so that rotation of the drive pulley by the drive motor causes the drive pulley to move along the belt thereby moving the platform frame between the extended position and the retracted position

12. The belt drive mechanism of Claim 1 1, further comprising two idler pulleys, the drive pulley being located between the two idler pulleys and the belt passing over the idler pulleys and drive pulley.

13. The belt drive mechanism of Claim 1 1, further comprising a reduction pulley that is larger than the drive pulley and a secondary belt that extends around the drive pulley and reduction pulley, the motor driving the drive pulley which in turn drives the reduction pulley whose rotation causes the platform frame to move between the extended position and the retracted position.

14. The belt drive mechanism of Claim 1 1 , wherein the drive motor is an electric motor.

15. The belt drive mechanism of Claim 12, wherein the drive motor is a hydraulic motor.

16. The belt drive mechanism of Claim 12, wherein the belt is releasably attached to the stationary frame.

17. A wheelchair lift comprising:

(b) a wheelchair platform pivotably coupled to the platform frame, the wheelchair platform being movable between a raised position and a lowered position;

(c) a belt drive extension and retraction mechanism coupled to the platform frame and a stationary frame in which the platform frame is movably mounted, the belt drive mechanism moving the platform frame between the extended position and the retracted positions, the belt drive extension and retraction mechanism including a belt that is attached at its opposing ends to the stationary frame, and at least one idler pulley and drive pulley rotatably attached to the platform frame, the belt drive extension and retraction mechanism also including a drive motor attached to the platform frame and coupled to the drive pulley, wherein the belt passes over the idler pulley and the drive pulley so that rotation of the drive pulley by the drive motor causes the platform frame to move along the belt between the extended position and the retracted position; and (d) an actuation mechanism coupled to the platform frame and the wheelchair platform to move the wheelchair platform between the raised and lower positions.

18. The wheelchair lift of Claim 18, wherein the belt is releasably coupled to the stationary frame.

19. The wheelchair lift of Claim 18, wherein the drive motor is an electric motor.