Patent Publication Number: US-2011049828-A1

Title: Wheelchair converted vehicle having independent rear suspension and method of manufacturing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/022,025, filed Jan. 29, 2008, which is based on and claims the priority to U.S. Provisional patent application No. 60/898,037 filed on Jan. 29, 2007, the disclosure of each of which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention is directed to a method of providing wheelchair access to an OEM (Original Equipment Manufacturer) vehicle having independent rear suspension. The invention is also directed to a wheelchair converted OEM vehicle comprising a trailing arm substitute. 
     BACKGROUND OF THE INVENTION 
     Presently there are no major automobile manufacturers that mass-produce highway vehicles that accommodate wheelchair access for private use. Consequently, these OEM vehicles must be modified and converted to properly accommodate wheelchair access. One problem encountered during the wheelchair accessibility conversion process of vehicles having independent rear suspension is that when the floor is sufficiently lowered to accommodate a side door wheelchair ramp system, the rear suspension trailing arm protrudes several inches into the vehicle side door opening area, preventing the installation and operation of a ramp system. If the trailing arm is simply shortened so as not to extend into the side door opening, the OEM rear suspension motion is substantially altered, providing for a lower quality performance and ride as compared to the unmodified OEM vehicle. Shortening the trailing arm also compromises the ride safety of the vehicle, which is unacceptable with today&#39;s vehicle safety standards, and typically voids the OEM vehicle warranty. The lowering of the floor of the vehicle to accommodate the ramp system also lowers the vehicle&#39;s OEM ground clearance. Raising the vehicle frame to obtain OEM ground clearance after the floor is lowered has the potential of significantly altering the OEM suspension motion and safety of the vehicle. 
     As can be seen, a need exists in the art for a method of efficiently converting an OEM vehicle having rear independent suspension in such a way to adequately accommodate a wheelchair ramp while substantially preserving the ride safety, performance, and quality of the OEM suspension, thereby producing a wheelchair accessible vehicle that is substantially as comfortable and safe to drive as the unmodified OEM vehicle. 
     It is an objective of this invention to provide a method for effectively producing a side door wheelchair accessible vehicle from an OEM vehicle, e.g., a minivan, while retaining the OEM suspension design, ride quality, and sufficient ground clearance. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method of converting an OEM vehicle having independent rear suspension into a wheelchair accessible vehicle with a side access wheelchair ramp. The present invention provides wheelchair access through the side door of a vehicle with a lowered floor while retaining the OEM suspension design intent and ride quality, and creating sufficient ground clearance. Further, the invention provides a converted rear suspension system that is compatible with the side door wheelchair access and a vehicle lowering system. The presently disclosed wheelchair access conversion process maintains the OEM wheel arc path and geometry through its operating range of motions (full bump and droop) while also reducing the physical space consumed by the rear suspension components to provide space for the wheelchair access system. 
     Preferably the disclosed conversion process includes the steps of: 
     a) providing an OEM vehicle having a vehicle body, at least one rear side door opening between a front door and a rear wheel of the vehicle body, and independent rear suspension, wherein the independent rear suspension comprises an OEM trailing arm having a first end and a second end, the OEM trialing arm being pivotally connected to the vehicle body at the first end and fixedly connected to a rear wheel OEM spindle at a second end, the OEM trailing arm being disposed in a longitudinal direction of the vehicle extending under the OEM floor beneath the rear side door opening allowing the OEM spindle to move through an OEM spindle arc path; 
     b) lowering the OEM vehicle floor in the rear side door opening area sufficiently to accommodate the side access wheelchair ramp; 
     c) replacing the OEM trailing arm with a trailing arm substitute, wherein the trailing arm substitute comprises an upper arm, a lower arm, a floor mount, and a spindle mount, the upper arm and lower arm each having a first end and a second end, the first end being pivotably connected to the floor mount and the second end being pivotably connected to the spindle mount, wherein the floor mount is connected to the lowered floor between the side door opening and the rear wheel so that the trailing arm substitute does not protrude into the side door opening and the spindle mount is connected to the rear wheel spindle; 
     d) installing a wheelchair access system that when deployed extends out the rear side door, thereby converting an OEM vehicle having independent rear suspension into a converted OEM wheelchair accessible vehicle having a side wheelchair access system. 
     The present invention is further directed to a converted OEM wheelchair accessible vehicle having a side access wheelchair system. The converted OEM wheelchair accessible vehicle preferably has: 
     a) a wheelchair converted vehicle body comprising a vehicle floor and at least one rear side door and rear side door opening, the rear side door and rear side door opening being between a front door and a rear wheel of the vehicle and the vehicle floor being sufficiently lower than the OEM floor to accommodate the side access wheelchair ramp; 
     b) a converted independent rear suspension, wherein the converted independent rear suspension comprises a trailing arm substitute which replaces an OEM rear trailing arm, wherein the trailing arm substitute comprises an upper arm, a lower arm, a floor mount, and a spindle mount, the upper arm and lower arm each having a first end and a second end, the first end being pivotably connected to the floor mount and the second end being pivotably connected to the spindle mount, wherein the floor mount is connected to the lowered floor between the side door opening and the rear wheel so that the trailing arm substitute does not protrude into the side door opening and the spindle mount is connected to the rear wheel spindle; and 
     d) a side wheelchair access system, wherein when deployed it extends out the rear side door. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an unconverted OEM vehicle having independent rear suspension, and further showing the internal OEM trailing arm extending under the vehicle floor located at the rear side door opening before the OEM floor is lowered. 
         FIG. 2  is a side view of the unconverted OEM independent rear suspension, including the OEM trailing arm that is disposed longitudinally extending under an OEM vehicle floor located at the rear side door opening of the vehicle, being pivotably attached to the vehicle body, while also being attached to the spindle. 
         FIG. 3  is a side view of a trailing arm substitute that includes an upper arm, a lower arm, a floor mount, and a spindle mount; the upper arm and lower arm each pivotably connected to the floor mount and also pivotably connected to the spindle mount. 
         FIG. 4  is a side view of the converted wheelchair accessible vehicle with a lowered floor in the rear side door opening area sufficient to accommodate the side wheelchair access system with the trailing arm substitute installed. 
         FIG. 5  is a partial rear view of the center of gravity, roll center, and roll couple of the unconverted OEM vehicle of  FIG. 1 . 
         FIG. 6  is a partial rear view of the center of gravity, roll center, and roll couple of the converted wheelchair accessible vehicle of  FIG. 4  after the floor has been lowered and the body lifted up off of the vehicle sub-frame sufficiently to maintain OEM ground clearance using body extensions. 
         FIG. 7  shows the converted and lowered vehicle floor with a side door ramp deployed. 
         FIG. 8  is a partial perspective view of a vehicle lowering system and a spring substitute installed on the converted wheelchair accessible vehicle of  FIG. 4 . 
         FIG. 9  is a side view of an alternate embodiment of the trailing arm substitute wherein the upper arm is the same length as the lower arm. 
         FIG. 10  is a side view of an alternate embodiment of the trailing arm substitute wherein the upper arm is longer than the lower arm. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be further described by way of example with reference to the accompanying drawings, which illustrate the invention for better understanding of its specific structures and advantages. The figures are not necessarily to scale, some features may be exaggerated or minimized to show details of particular components or processes. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     As shown in the FIGS., the present invention is directed to a converted wheelchair accessible vehicle  30  having independent rear suspension  20  with a side access wheelchair ramp system  40  and also to a method of converting an OEM vehicle  10  into such a wheelchair accessible vehicle  30 . The method advantageously allows the OEM suspension  20  design intent and ride quality to be maintained while providing appropriate wheelchair access to the vehicle. 
     In general, the conversion process includes the steps of: 
     a) providing an OEM vehicle  10  having independent rear suspension  20  comprising an OEM trailing arm that protrudes into the side door opening if the floor  15  is lowered; 
     b) lowering the OEM vehicle floor  15  sufficiently to provide increased head room for the wheelchair occupants and to accommodate the side access wheelchair ramp  41 ; 
     c) replacing the OEM trailing arm  21  with a trailing arm substitute  50  that does not protrude into the side door opening  12 ; and 
     d) installing a wheelchair access system  40  that when deployed extends out the rear side door  16 . 
     As shown in  FIG. 1 , the OEM vehicle  10  used for the conversion process has a vehicle body  11 , at least one rear side door opening  12  between a front door  13  and a rear wheel  14  of the vehicle body  11 , and independent rear suspension  20 . The independent rear suspension  20  comprises an OEM trailing arm  21  on each side of the OEM vehicle  10 . As shown in  FIG. 2 , the OEM trailing arm  21  generally has a first end  22  and a second end  23 . The OEM trailing arm  21  is pivotally connected to the vehicle body  11  at the first end  22  and fixedly connected to a rear wheel OEM spindle  24  at a second end. The OEM trailing arm  21  is typically disposed in a longitudinal direction of the vehicle  10  extending under an OEM vehicle floor  15  beneath the rear side door opening  12  of the vehicle  10  allowing the OEM spindle  24  to move through an OEM spindle arc path  25 . Therefore, if the OEM vehicle floor  15  is lowered the OEM trailing arm  21  would necessarily protrude into the rear side door opening  12 . 
     The OEM vehicle body  11  can be any vehicle body with the rear side door opening  12 . In a preferred embodiment, the vehicle body  11  is a van, and more preferably a minivan. In one embodiment the vehicle body  11  is a unibody designed to disseminate load-bearing structural elements throughout the entire body of the vehicle  10 . An example of an OEM vehicle  10  having a suitable unibody is the 2005 Honda ODYSSEY. 
     Trailing Arm Substitute 
     As shown in  FIG. 3 , the trailing arm substitute  50  typically comprises an upper arm  51 , a lower arm  52 , a floor mount  53 , and a spindle mount  54 . The upper arm  51  and lower arm  52  each have a first end  55  and a second end  56 . The first end  55  of each is preferably pivotably connected to the floor mount  53  and the second end  56  of each is also preferably pivotably connected to the spindle mount  54 . The floor mount  53  is connected to the lowered vehicle floor  28  between the side door opening  12  and the rear wheel  14  so that the trailing arm substitute  50  does not protrude into the side door opening  12 . The spindle mount  54  is connected to the rear wheel spindle  24  as shown in  FIG. 3 . 
     The trailing arm substitute  50  is designed such that the upper arm  51  is shorter than the lower arm  52 ; in the alternative the upper arm  51  is longer than the lower arm  52 ; or the upper arm  51  can be the same length as the lower arm  52 . The trailing arm substitute  50  is designed to control the movement of the OEM spindle  24  so as to mimic the OEM conditions in order to maintain the OEM ride quality and OEM wheel frequency. 
     In a preferred embodiment, each of the OEM trailing arms  21  are replaced with a trailing arm substitute  50 . 
     Referring to  FIG. 2 , the OEM spindle  24  is typically attached to the vehicle body  11  with an OEM trailing arm  21  of a fixed radius. This arm  21  is fixed to the spindle  24  and pivots at the first end  22 , which is the point of attachment to the vehicle body  11  and the center of the spindle arc path  25 . This allows the spindle  24  to move through the defined spindle arc path (first arc path)  25 . The movement of the OEM spindle  24  is further characterized by the rotation of the spindle  24  relative to the vehicle body  11  as it travels along the arc path  25 . This can be defined as maintaining a constant arc path (second arc path)  25   a  of a second point on the spindle  24  (for example, the point of attachment of the toe-link) of which the center is coincident with the arc path  25  traced by the spindle center  24   a.    
     By replacing the OEM trailing arm  21  with a specially designed trailing arm substitute  50 , shown in  FIGS. 3-4 , the movement of the spindle  24  can be preserved within a certain boundary. Preferably the boundary is defined by an upper limit, referred to as “full bump,” and a lower limit, referred to as “full droop”. As measured at OEM ride-height, full bump is typically +3 to +4 inches, preferably +3 inches, and full droop is −1.5 to −3 inches, preferably −2 inches. Outside of these two limits, full bump and full droop, the new arc path may deviate from the OEM arc path  25  as it will not effect the ride quality of the vehicle. Preferably the trailing arm substitute  50  is designed so that within full bump and full droop the OEM arc path  25  and the new arc path are substantially identical. 
     The rotation of the spindle  24  relative to the vehicle body  11  is substantially reproduced to match OEM behavior between the full bump and the full droop limits. Outside of these limits, the rotation may vary from OEM behavior. 
     In one embodiment, the movement of the spindle  24  attached to the trailing arm substitute  50  produces an arc path within 0.5 inches, more preferably within 0.25 inches, of the OEM arc path  25  at each position between a bump of +3 inches and a droop of −2 inches as measured from OEM ride-height. 
     The behavior of the rear wheels as they travel through their full range of motion (between full bump and full droop) are characterized in two primary ways: toe and camber. Camber refers to the tilting of a wheel/tire. If the top of the tire is leaning outward from the car, then this is called “positive” camber or if the top of the tire is leaning in toward the car, this is called “negative” camber. Camber is typically measured in degree of tilt. For example, 2 degrees of positive camber means the top of the wheel is leaning outward 2 degrees. As the tire moves up and down between full bump and full droop the camber changes. A camber curve is derived based on the degree of camber as the wheel moves vertically. Toe, on the other hand, is the angle which the axis of rotation of the wheel makes with a horizontal axis extending perpendicular to the central longitudinal axis of the vehicle. The angle is negative when the front of the wheel is “toed-in”, and positive when the front of the wheel is “toed-out.” 
     Preferably the converted vehicle  30  has a rear wheel camber curve within ±0.75 degrees, more preferably ±0.05 degrees or most preferably less than ±0.03 degrees per inch, of the vehicle&#39;s OEM rear wheel camber curve at each position between a bump of 3 inches and a droop of 2 inches as measured from OEM ride-height. Preferably the converted vehicle  30  also has a rear wheel toe curve within ±0.3 degrees per inch, more preferably ±0.06 degrees per inch, or most preferably within ±0.03 degrees per inch of the vehicles OEM rear wheel toe curve at each position between a bump of +3 inches and a droop of −2 inches measured from OEM ride-height. 
     In one specific embodiment, the converted vehicle  30  with the trailing arm substitute  50  has a toe curve of ±0.01 degrees per inch of the OEM toe curve and a new camber curve within ±0.05 degrees per inch of the OEM camber curve. 
     The use of the trailing arm substitute  50  as taught herein, allow for a more compact overall suspension system  20 , while maintaining the movement and behavior of the OEM spindle  24 . This results in the preservation of the ride quality and safety of the converted vehicle  30  while increasing the amount of available space for wheelchair passengers and the ramp system  40 . 
     Spring Substitutes 
     To preserve the OEM vehicle  10  handling dynamics and proper balance of the ride quality between the front and rear suspensions, the rear OEM springs  70  are replaced with spring substitutes  71 , as shown in  FIG. 8 . The spring substitute  71  typically has a longer length and a higher spring rate than the OEM spring  70 . This allows the extra weight incorporated into the converted vehicle  30  to be carried at the proper ride height while maintaining the proper wheel frequency. The spring substitutes  71  provide a new spring rate, which can be calculated using the converted vehicle&#39;s 30 weight and a target wheel frequency. Preferably the target wheel frequency is between 1.0 and 1.4 cycles per second, more preferably the between 1.1 and 1.3 cycles per second and most preferably about 1.2 cycles per second in order to provide for a comfortable ride. Preferably, the rear spring substitute  71  is longer and has a different spring rate than the OEM suspension spring  70  to maintain an OEM wheel frequency in view of the added weight of the converted vehicle  30 . 
     Vehicle Lowering System 
     In a preferred embodiment, the conversion process also includes installation of a vehicle lowering system  57  which compresses the rear spring substitutes  71  to lower the vehicle body  11  to the ground (see  FIG. 8 ). In this embodiment, the rear spring substitutes  71  have specific parameters to prevent plastic deformation during maximum compression of the spring substitutes  71  due to the vehicle lowering system  57 , thereby returning to a pre-compression height after the compression in the vehicle lowering process and maintaining the OEM wheel frequency. 
     Lowering the OEM Vehicle Floor 
     Generally, during the conversion process the OEM vehicle floor  15  is lowered sufficiently to provide increased head room and to accommodate the side access wheelchair ramp system  40  at least in the rear side door opening area  12 . Preferably the vehicle floor  15  is also lowered in the front of the vehicle to allow the wheelchair bound individual the ability to access the front of the vehicle  30  and drive the vehicle  30  if appropriate. 
     The OEM vehicle floor  15  is typically lowered by at least 4 inches; more preferably by at least 6 or 8 inches and most preferably by at least 10 inches. In one specific embodiment, the OEM vehicle floor  15  is lowered between 10 and 12 inches in the rear side door opening area  12  and 6 to 7 inches in the front area of the vehicle  10 . 
     In a preferred embodiment, the conversion method further includes raising the vehicle body  11  to maintain the OEM ground clearance of the suspension subframe  18  and achieve the desired ground clearance of the lowered floor  28 . Raising the vehicle body  11  instead of the vehicle frame/subframe  18 , allows the OEM roll center to be substantially maintained while providing sufficient ground clearance. Preferably the step of raising the vehicle body is accomplished by using body extensions  58  to raise the vehicle body  11  while allowing the suspension subframe  18  to remain at the OEM height as shown in  FIGS. 3 and 6 . 
     As shown in  FIG. 5 , the location of the roll center in the OEM vehicle  10  is effected by the mounting points for the upper control arms (line AB) and lower control arms (line CD) of the independent rear suspension  20  in the OEM vehicle  10 . The angle of these control arms determine the points where they intersect which in turn defines the location of the roll center.  FIG. 6  shows the center of gravity, roll center, and roll couple of a converted wheelchair accessible vehicle  30  after the floor  15  has been lowered and the vehicle body  11  lifted up off of the vehicle sub-frame  18  to achieve the desired ground clearance of the lowered floor  28 . By maintaining the OEM angle of the upper and lower control arms, the OEM roll center location is maintained. 
     Keeping the roll center in the OEM location after conversion also maintains the roll-couple, the imaginary line between the roll center and the vehicle&#39;s center of gravity. By preserving the roll couple, the rear suspension will stay in balance with the front suspension, thereby preserving the overall OEM vehicle handling performance. 
     Raising the vehicle body  11  will affect the mounting points of the suspension that are rigidly attached to the vehicle body  11 . These mounting points must be relocated to restore the upper and lower control arms to their original angles, thereby preserving the location of the roll center. This is achieved by using the body extensions  58  to raise the vehicle body  11 . 
     Preferably the vehicle body  11  is raised by at least 2 to 3 inches, more preferably by at least 3 to 6 inches. In one particular embodiment, the rear of the vehicle body  11  is raised by 4.5 inches, while the front of the vehicle body  11  is raised by 1 to 4 inches, more preferably by at least 2.5 to 3 inches. In a preferred embodiment, the body extensions  58  are designed so that the OEM bolts and materials can be used, thereby maintaining quality standards. Typically the body extensions  58  are welded to the vehicle body  11 . The body extensions  58  are advantageously designed to lower the OEM body  11  and OEM subframe  18  connections points so that after the vehicle body  11  is raised, the OEM roll center location is substantially maintained within the allowed variations for the OEM roll center specifications. 
     Wheelchair Access System 
     As shown in  FIG. 7 , the wheelchair access system  40  is generally designed to extend out the rear side door  16  when deployed. In the illustrated embodiment of  FIG. 7 , the wheelchair access system includes a ramp  41 . Preferably, the ramp  41  is at least 30 inches wide, and more preferably at least 34 inches wide. An example of a suitable ramp is the VMI NORTHSTAR ramp. It will be apparent to one of ordinary skill in the art from this disclosure that the wheelchair access system can be any suitable access system that allows for the effective and safe transfer of the wheelchair from the vehicle, such as a platform lift. 
     As shown in  FIGS. 4 and 7  and discussed above, the present invention further encompasses the converted OEM wheelchair accessible vehicle  30  having a side access wheelchair ramp. The wheelchair converted vehicle body  11  has a lowered vehicle floor  28  and at least one rear side door  16  and rear side door opening  12  both being between a front door  13  and a rear wheel  14  of the vehicle  30  and the lowered vehicle floor  28  being sufficiently lower than the OEM floor  15  to accommodate the side access wheelchair ramp  41 . 
     Advantageously, the converted vehicle  30  also has a converted independent rear suspension  49  comprising a trailing arm substitute  50  which replaces an OEM rear trailing arm  21  as discussed above. The converted vehicle  30  generally further includes a side access wheelchair ramp system  40 , wherein when the ramp  41  is deployed, it extends out the rear side door  16 . 
     The present invention will now be illustrated by the following non-limiting example. It is to be understood that the foregoing describes preferred embodiments of the present invention and that modifications may be made therein without departing from the spirit or scope of the present invention as set forth in the claims. 
     Example 
     Conversion of 2005 Honda Odyssey 
     A 2005 Honda Odyssey having independent rear suspension was obtained. The OEM vehicle floor was lowered. The floor  15  was lowered by approximately 11 inches, between 10 to 12 inches, in the rear area and between 6 and 7 inches in the front area of the converted vehicle  30 . 
     The OEM trailing arm  21  was removed and replaced by a trailing arm substitute  50  comprising an upper arm  51 , a lower arm  52 , a floor mount  53 , and a spindle mount  54 . The upper arm  51  and lower arm  52  are pivotably connected to the floor mount  53  and pivotably connected to the spindle mount  54 . In this specific embodiment, the upper arm  51  is substantially shorter than the lower arm  52 . 
     After lowering the vehicle floor  15 , the vehicle body  11  was lifted up by installing body extensions  58  in order to maintain the OEM ground clearance of the suspension subframe  18  and achieve the desired ground clearance of the lowered floor  28 . The body extensions  58  were welded to the body frame and the OEM bolts were used to attach the vehicle body  11  to the subframe  18  using the body extensions  58  as the new contact points between the vehicle body  11  and the subframe  18 . The body extensions  58  were 4.5 inches high in the back of the vehicle and 3 inches high in the front of the vehicle. 
     A vehicle lowering system was also installed in the vehicle as was a wheelchair ramp system  40  that when deployed extended out the rear side door. A VMI NORTHSTAR ramp was used in this particular example. 
     The OEM rear springs  70  springs were replaced with spring substitutes  71  having a spring rating of 6001b/in having a compressed height at 2080 lbs at 14.5 inches.