Patent Publication Number: US-10758436-B2

Title: Powered wheelchair, wheelchair powering device and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/942,866, filed on Apr. 2, 2018 and titled “POWERED WHEELCHAIR, WHEELCHAIR POWERING DEVICE AND METHOD,” which claims priority to and the benefit of U.S. Provisional Patent Application No. 62/480,008, filed on Mar. 31, 2017 and titled “POWERED WHEELCHAIR, WHEELCHAIR POWERING DEVICE AND METHOD,” the entirety of each of which is incorporated herein by this reference. 
    
    
     BACKGROUND 
     Wheelchairs are available in a variety of different forms. One of the most basic distinctions is between “powerchairs,” which are wheelchairs powered by batteries and electric motors, and manual wheelchairs, which are self-propelled by the wheelchair user or by an attendant pushing the chair from behind. Many manual wheelchairs are designed to be foldable so that the owner/user can reduce the profile of the wheelchair for easier storage, transport, and/or maneuvering of the wheelchair. For example, a user may fold a wheelchair so it can be placed in the trunk of a car, in a closet, or in another convenient storage location. 
     Powerchairs incorporate batteries and electric motors to provide propulsion to the wheelchair. Although powerchairs provide motorized assistance to the chair user, they are typically much heavier than their manual chair counterparts, which makes them much more difficult to transport, store, or carry/maneuver. In addition, powerchairs are typically larger than manual wheelchairs and have no folding capabilities, which exacerbates the challenges in storing, transporting, and carrying/maneuvering the powerchairs. 
     BRIEF SUMMARY 
     The present disclosure describes devices and systems for upgrading a manual wheelchair to a hybrid wheelchair selectively capable of both manual operation and motor-powered operation. In certain embodiments, a wheelchair upgrade device may be integrated with a standard foldable manual wheelchair with limited alterations required for the manual wheelchair. In certain embodiments, a wheelchair upgrade device is configured so that when coupled to a foldable manual wheelchair, the foldable manual wheelchair maintains its ability to fold down for easier storage, stowing, and/or transport. This enables the selective bimodal use of the wheelchair without reducing the beneficial folding capabilities of the wheelchair. In addition, the wheelchair upgrade device is lightweight, with minimal impact on the ability to store, transport, and/or maneuver the upgraded wheelchair after attachment to the wheelchair upgrade device. 
     Additional features and advantages will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the embodiments disclosed herein. The objects and advantages of the embodiments disclosed herein will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing brief summary and the following detailed description are exemplary and explanatory only and are not restrictive of the embodiments disclosed herein or as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe various features and concepts of the present disclosure, a more particular description of certain subject matter will be rendered by reference to specific embodiments which are illustrated in the appended drawings. Understanding that these figures depict just some example embodiments and are not to be considered to be limiting in scope, various embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  illustrates a standard foldable manual wheelchair; 
         FIGS. 2A through 2C  illustrate a typical folding procedure for a standard foldable manual wheelchair; 
         FIGS. 3A and 3B  illustrate exemplary embodiments of a wheelchair upgrade device; 
         FIGS. 4 and 5  illustrate additional views of the wheelchair upgrade device, showing an encasement for housing the motor and drive assembly components and showing a protective cover surrounding the roller member; 
         FIG. 6  illustrates another view of the wheelchair upgrade device showing the motor and other drive assembly components; 
         FIG. 7A through 7C  illustrates the wheelchair upgrade device coupled to a foldable wheelchair, with  FIG. 7B  showing the device in a disengaged state and  FIG. 7C  showing the device in an engaged state; 
         FIG. 8  illustrates a wheelchair upgrade system integrated with a foldable wheelchair, transforming the wheelchair into a hybrid wheelchair capable of selective bimodal operation; and 
         FIG. 9  illustrates a foldable wheelchair with which the wheelchair upgrade system has been integrated successfully folded without detaching the wheelchair upgrade system. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes devices and systems for upgrading a manual wheelchair into a hybrid wheelchair selectively capable of both manual operation and motor-powered operation. In certain implementations where the upgraded wheelchair is a foldable wheelchair, the wheelchair upgrade device is configured to beneficially maintain the folding capabilities of the wheelchair, so that the wheelchair continues to provide relatively easy storage, transport, and/or maneuvering, even after upgrading. 
       FIG. 1  illustrates a standard manual wheelchair  10 . As shown, the wheelchair  10  includes a seat  12 , backrest  14 , footrests  16 , rear wheels  18 , front casters  20 , and push handles  22 . The rear wheels  18  are each connected to a corresponding pushrim  24 , which may be grabbed by a user to propel and move the wheelchair. A pair of brakes  26  are also included. As shown, the brakes  26  are typically positioned on a portion of the frame underneath the seat  12  and in front of the corresponding rear wheel  18 . The brakes  26  are operated by pushing or pulling a lever to bring the brake out of or into contact with the rear wheel  18 . 
       FIGS. 2A through 2C  illustrate a typical process for folding a standard manual wheelchair. As shown, the footrests  16  are folded away from the center of the wheelchair. The seat  12  is then pulled upwards and/or the push handles  22  (or other portion of the outer frame) are pushed inwards to allow the wheelchair to collapse toward its center. The standard wheelchair  10  typically has a set of cross members  28  as part of the wheelchair frame when the wheelchair is in an unfolded configuration. These cross members  28  are often diagonally positioned to form an X-shape, as shown. The cross members  28  must be allowed to pivot and move without hindrance to allow the wheelchair to be adjusted to the folded configuration. 
       FIG. 3A  illustrates an exemplary embodiment of a wheelchair upgrade device  100 . The illustrated device  100  may be coupled to a suitable section of the frame of a receiving wheelchair and positioned to selectively provide motor-powered operation of the wheelchair. The device shown in  FIG. 3  may be placed on one side of the receiving wheelchair (e.g., the left side) while another mirror-image version of the device is placed on the opposite side of the receiving wheelchair. Typically, both sides of the receiving wheelchair will be coupled to an upgrade device so that both wheels of the wheelchair will have the capability for selective motor-powered operation, though the embodiments described herein also include embodiments where only one side of a wheelchair is upgraded. 
     The illustrated embodiment includes an attachment mechanism to enable attachment of the device to a foldable wheelchair. The illustrated embodiment includes a coupling bracket  110  with a slotted section  112  to allow the use of fastening hardware (e.g., one or more screws, rivets, nuts and bolts, pins, etc.) to attach the coupling bracket  110  to a suitable portion of the wheelchair frame. Other embodiments may additionally or alternatively include one or more clamps, clasps, ties, friction fitting members, other fastening mechanisms, or combinations thereof. In some embodiments, the device  100  may be welded, adhered, or otherwise more permanently attached to the frame of the receiving wheelchair, though presently preferred embodiments are configured for detachable coupling to the receiving wheelchair. 
     Foldable wheelchairs will typically include one or more pre-existing holes or other receiving structures on a portion of the frame underneath the seat to allow attachment of braking components. Because the wheelchair upgrade device  100  is beneficially capable of providing braking functionality in addition to providing motorized power to the wheelchair, the standard brakes may be removed and the receiving holes/structures may be utilized for mounting of the upgrade device  100 . Alternatively, if such receiving structures are not available on a particular wheelchair, a clamp-on (e.g., through lever lock clamp or screw-tightened clamp) attachment structure may be utilized. 
     Preferred upgrade device embodiments are configured to sufficiently attach to the receiving wheelchair at a single wheelchair frame member. For example, the illustrated device  100  is capable of being suspended at a position below the seat of the receiving wheelchair without requiring further underlying support or attachment to additional members of the wheelchair frame. The simple and effective coupling arrangement allows the device  100  to be properly positioned with minimal interference with the wheelchair frame and other wheelchair components, which in turn allows for ready folding and adjusting of the wheelchair without interference from the attached upgrade device. The illustrated embodiment is also capable of attachment to a foldable wheelchair without requiring the installation of additional wheelchair frame members. 
     The illustrated embodiment also includes a motor  102  operatively coupled to a roller member  108 . As explained in more detail below, the roller member  108  is configured to be mechanically pressed against a corresponding tire of the receiving wheelchair. In such a position of contact, rotation of the roller member  108  drives rotation of the tire via the friction force between the roller member  108  and the contacted wheel. The roller member  108  is also able to function as a brake. For example, when the motor  102  is not driving rotation of the roller member  108 , the roller member  108  can be contacted against the corresponding tire to slow and/or prevent rotation of the wheel. In this manner, the roller member  108  is able to function as both a means for transmitting power to the wheel and as a brake. 
     The illustrated device will typically include a motor housing  104  (see  FIGS. 4 and 5 ). For clarity, the motor housing  104  is removed in this view to expose the interior motor and power transmission components. In some embodiments, the housing  104  is sealed to prevent unintentional contact with the interior components. In some embodiments, the motor housing  104  is sized to be compact and readily integrated with the receiving wheelchair. For example, the motor housing may have a width of about 2 to 5 inches, or about 3.5 inches, may have a length of about 3 to 7 inches, or about 5 inches, and a height/depth of about 2 to 5 inches, or about 3.5 inches. Thus, the motor housing may have a volume of about 45 to 85 cubic inches, or about 65 cubic inches. 
     The motor  102  may be any motor (or set of motors) of suitable power for driving rotation of the wheelchair wheel to which it is operatively coupled, or for at least assisting a user to make manual rotation of the wheel easier than in the absence of assistance from the motor  102 . In presently preferred embodiments, the motor  102  is a brushless, high RPM motor. In one example, a suitable motor has a max power rating of 800 w, a Kv rating of 600 rpm/V, a max current of 54 A, a voltage rating of 14.8 v (4 s), an ESC of 80 A, and a no-load current of 0.6 A. It will be understood that other motors having other ratings may also be utilized according to preferences and particular application needs. 
     The illustrated embodiment includes a power transmission assembly  106  for transmitting power from the motor  102  to the roller member  108 . The illustrated embodiment shows a series of pulleys to be fitted with a suitable belt. Alternative embodiments may additionally or alternatively include one or more gears, sprockets, tracks, rollers, racks (e.g., gear racks), worm gears, worms, clutches, universal joints, right-angle drives, bearings, gear boxes, and/or other power transmission components known in the art. In preferred embodiments, at least some of the components of the power transmission assembly  106  are formed from a lightweight material. For example, the pulleys (or the gears or other components as the case may be for a particular embodiment) may be formed from nylon or other suitable polymer material. 
     In the illustrated embodiment, the power transmission assembly is configured so that the shaft of the motor  102  is substantially parallel to the axis of the roller member  108 . This arrangement provides effective power transmission to the roller member  108 , and allows the motor  102  and roller member  108  to be positioned relative to one another in a manner that allows for compact and discreet integration of the device  100  with the receiving wheelchair. In particular, it has been found that in preferred embodiments utilizing relatively high RPM motors and relatively high gear ratios, aligning the motor shaft and the roller member  108  to be substantially parallel to one another (as opposed to a 90-degree offset, for example) enables effective operation of the device and propulsion of the contacted wheel. 
     The illustrated embodiment also includes an adjustment mechanism  114  operatively coupled to at least the roller member  108  to control movement of the roller member  108  toward or away from the corresponding wheelchair wheel. In the illustrated embodiment, the adjustment mechanism  114  includes links  120  disposed to form a kinematic change-point mechanism (see  FIGS. 7B and 7C ). Alternative embodiments may additionally or alternatively include other link elements, lever components, pivot attachments, limit pins, and/or other lever components known in the art. The adjustment mechanism  114  also includes a tab  121  for limiting the rotation of the link assembly too far beyond the change-point (when the links are approximately linearly aligned). 
     The illustrated adjustment mechanism  114  includes a lever  116  coupled to a roller member bracket  118 . The roller member bracket  118  is rotationally attached to the mounting bracket  110  in a manner that allows the roller member bracket  118  to pivot relative to the mounting bracket  110 . The roller member  108  passes through the roller member bracket  118  so that pivoting of the roller member bracket  118  also causes pivoting of the roller member  108  relative to the mounting bracket  110  (and relative to the wheelchair wheel). 
     In the illustrated embodiment, the roller member bracket  118  is rotationally linked to the motor housing  104  so that both the roller member bracket  118  and the motor housing  104  rotate together, along with the lever  116 , when the lever  116  is adjusted. As shown, the motor  102  is positioned so that when the device  100  is coupled to a receiving wheelchair, the motor shaft is substantially horizontally oriented. The motor  102  is also positioned so that the motor shaft maintains the same angular tilt with respect to vertical and horizontal axes without respect to the position of the lever  116 . For example, the motor shaft does not tilt upwards or downwards depending on whether the lever  116  is pushed forward or pulled back. This beneficially allows the device components to be positioned in a manner that allows for compact and discreet integration of the device  100  with the receiving wheelchair, and enables effective power transmission and propulsion of the contacted wheel. 
     The roller member  108  may be formed from any suitable material capable of providing sufficient friction contact with a corresponding wheelchair tire, such as a metal, polymer, or ceramic material. In preferred embodiments, the roller member  108  is formed from aluminum or an aluminum alloy. Such lightweight materials provide the roller member  108  with effective power transmission and braking capabilities while also being relatively lightweight. In an embodiment, the outer diameter surface of the roller member  108  may be etched or provided with a surface finish that increases the frictional forces so as to better apply torque to the outer perimeter of the tire of the wheelchair. 
     In some embodiments, the roller member  108  optionally includes a sleeve  122  disposed over at least a portion of the surface of the roller member  108 . The sleeve  122  can beneficially minimize tire wear by acting as a sacrificial material that wears faster than the material of the wheelchair tire or about as fast as the material of the wheelchair tire. For example, the sleeve  122  may be formed from a rubber material, polyurethane, urethane, nylon, polyether block amide (PEBA), or other suitable polymer material. The sleeve  122  may also be fitted with a keyway, or a spring pin, or other locking mechanism so as to hold the sleeve rotationally fixed to the roller member  108 . Preferably, the sleeve material has a durometer that is substantially equal to or lower than the durometer of the wheelchair tire. Typically, a wheelchair tire will be formed from rubber or urethane. 
     Some embodiments, such as shown in  FIG. 3B , may also include a roller guard mechanism coupled to the roller member  108  for selectively impeding rotation of the roller member  108 . In some embodiments, the sleeve  122  can function as the guard mechanism. A lever (e.g., lever clamp  180 ) can be operatively coupled to the guard mechanism so that when appropriately adjusted, the guard mechanism is forcefully pushed against the roller member  108  to prevent rotation, and to thereby also prevent movement of the wheelchair wheels. 
     The illustrated embodiment is configured to provide a high gear ratio between the wheelchair tire and the motor  102 . In the illustrated embodiment, the motor shaft is geared up by a factor of 3. The roller member  108  has a diameter of approximately 1 inch. The ratio between the roller member  108  and a standard wheelchair wheel diameter (about 24 inches) is therefore about 24. The overall gear ratio between the wheelchair wheel and the motor  102  is therefore about 72:1. 
     Alternative embodiments may include different assemblies to achieve the same gear ratio, or may have different overall gear ratios. For example, the roller member  108  may be geared up relative to the motor shaft by a factor of 1, 2, 3, 4, 5, 7, 10, or a factor within a range with endpoints defined by any two of the foregoing values. The roller member  108  may have a diameter of about 0.5 inches, 0.75 inches, 1 inch, 1.25 inches, 1.5 inches, 2 inches, 3 inches, 4 inches, or a diameter within a range having endpoints defined by any two of the foregoing values. The overall gear ratio between the wheelchair wheel and the motor shaft may be about 6:1, 15:1, 30:1, 45:1, 60:1, 75:1, 90:1, 105:1, 120:1, or 135:1, for example. 
       FIGS. 4 through 6  illustrate various views of the wheelchair upgrade device  100 .  FIGS. 4 and 5  show the housing  104  for housing the motor and other power transmission assembly components. The configuration shown in  FIGS. 4 and 5  also includes a cover  109  configured to conceal the portions of the roller member  108  that do not need to be contacted against the wheelchair wheel. This can prevent accidental touching of an operating roller member  108  during operation of the device.  FIG. 6  shows another view of the device  100  without the housing  104  to better illustrate the motor  102  and other components of the power transmission assembly  106 . 
       FIG. 7A  illustrates the upgrade device  100  coupled to a foldable wheelchair  200 . Although the Figure shows the upgrade device  100  on only one side of the wheelchair  200 , it will be understood that a mirror-image version of the upgrade device  100  may be coupled to the opposite side of the wheelchair as well to provide selective bimodal operation to both rear wheels of the wheelchair  200 . 
     In the illustrated embodiment, the upgrade device  100  is coupled to the wheelchair frame so that the device is suspended below the seat  202  with the roller member  108  positioned in front of the corresponding wheel. In this preferred position, the upgrade device  100  is easily accessible to the wheelchair user while the user is seated in the wheelchair. The illustrated position of the upgrade device  100  is also where wheelchair brakes are commonly placed. The upgrade device  100  may therefore function as a replacement for the typical wheelchair braking mechanism. In some embodiments, the wheelchair omits any other braking components in the position of the upgrade device (e.g., omits any additional braking device attached to the same frame member as the upgrade device). 
     In addition, the wheelchair upgrade device  100  may be adjusted, attached to, or detached from the wheelchair frame while a user sits in a wheelchair, without the need for the user to move on and off of the wheelchair whenever an upgrade device  100  is adjusted, attached, or detached. The wheelchair upgrade device  100  is also capable of being attached and/or detached without requiring removal or adjustment of the wheelchair wheels, and without requiring added rims or added support frames on the wheelchair. 
     As explained above, the upgrade device  100  is capable of acting as both a brake and a source of motorized power. In the illustrated position, the lever  116  is in a pushed forward positon, bringing the roller member  108  into contact with the wheelchair tire  204 . In this position, the upgrade device  100  can act as a brake (when the motor is not driving the roller member  108 ) or as the source of motorized power (when the motor drives rotation of the roller member  108 ). The lever  116  may be pulled back to move the roller member  108  away from the wheelchair tire  204 , thereby allowing the wheelchair to be operated/propelled manually. 
     In alternative embodiments, an upgrade device may be positioned at other locations of the receiving wheelchair. For example, the upgrade device  100  may be suspended above a lower wheelchair frame member (such as frame member  206 ) instead of suspended below an upper (below the seat) wheelchair frame member  208 , may be attached at or near an armrest  210  so as to be positioned above the wheelchair tire  204 , or may be attached at or near a rear frame member  212  so as to contact a rearward portion of the wheelchair tire  204 . 
     Although the exemplary illustrated embodiment includes a lever  116  for controlling adjustment of the device  100 , alternative embodiments may additionally or alternatively include one or more knobs, grips, turn-dials, or other suitable controls capable of actuating mechanical adjustment of the other components of the upgrade device  100 . 
       FIGS. 7B and 7C  show side views of the device as it is coupled to a wheelchair, with  FIG. 7B  showing the device disengaged from the wheelchair wheel  204  and  FIG. 7C  showing the device engaged against the wheelchair wheel  204 . As shown in  FIG. 7B , the lever is pulled toward the user, which puts link members  120   a  and  120   b  out of linear alignment. This rotates the motor housing and roller member bracket  118  in a position where the roller  108  is disengaged from the wheelchair wheel  204 . When the lever is pushed forward to the position shown in  FIG. 7C , the links  120   a  and  120   b  are brought into greater linear alignment. This causes the motor housing and the roller member bracket  118  to rotate relative to the coupling bracket  110  and thereby engage against the wheelchair wheel  204 . 
     In the engaged position, the lever may be positioned to place the link assembly just past the change-point. For example, when pushing the lever forward from the disengaged position of  FIG. 7B  to toward the engaged position of  FIG. 7C , the link members  120   a  and  120   b  are brought to the change point where they are substantially linear. At this point the roller  108  is pressed against the wheelchair wheel  204  with maximum force. A slight amount of additional pushing of the lever puts the link members  120   a  and  120   b  just past the change point on the other side, to where they are just slightly out of alignment as shown in  FIG. 7C . This beneficially keeps the device in a firm engaged state against the wheelchair wheel  204  while also minimizing risk of unintentionally slipping out of engagement. The stop tab  121  limits the link assembly from being pushed too far past the change point when the lever is pressed forward. The stop tab  121  also provides structure for rotating link member  120   b  when the lever is pulled back toward the user. 
       FIG. 8  illustrates a foldable wheelchair  200  showing an exemplary wheelchair upgrade system integrated with the foldable wheelchair  200 . As shown, the upgrade device  100  is attached at the exemplary position shown in  FIG. 7 . A battery  150  is positioned underneath the arm rest  210  and is wired or otherwise operatively coupled to the motor of the upgrade device  100  (and optionally to the controller  160  as well). The battery  150  may alternatively be positioned at other locations. For example, the battery  150  may be positioned underneath the seat  202  and/or may be directly connected to the upgrade device  100  (e.g., on the motor housing). In some embodiments, the battery  150  may be attached to a frame member of the wheelchair, such as lower frame member  206 , upper frame member  208 , or rear frame member  212 . Preferably, however, the location of the battery  150  is selected so as not to interfere with folding of the wheelchair  200 . 
     The battery  150  may be any battery or other power source capable of providing sufficient power to the motor of the upgrade device  100 . In presently preferred embodiments, the battery  150  is a lithium-ion polymer battery, which provides effective power with relatively little added weight. The battery  150  may also be sized as needed to provide desired levels of power, though preferred battery sizes are small enough to avoid interference with folding of the wheelchair. In one embodiment, the battery  150  has a size of about 5.5 inches by 1.75 inches by 1.0 inch. Although a single battery  150  is shown, it will be understood that multiple batteries may also be utilized to provide power to the motor(s) of the upgrade device(s). It will be understood that other types and/or sizes of batteries may be utilized according to particular application needs or preferences. 
     The illustrated upgrade system also includes a controller  160  that is communicatively linked to the motor of the upgrade device  100 . The controller can include one or more joystick, directional paddle, button assembly, accelerometer device, and/or other manipulatable device capable of receiving inputs from the wheelchair user. The controller  160  may be directly wired to the upgrade device  100  or may be wirelessly linked (e.g., via Bluetooth, infrared signal, and/or other suitable connection). The controller  160  sends received input to the motor of the upgrade device  100  to control at least the rotation speed of the roller member, thereby controlling the movement of the contacted wheel. The controller  160  may be attached to the wheelchair or may be a separate, detached component. In embodiments in which it is attached, it may be attached to an arm rest, to a portion of the frame, or to another suitable location where a user can readily reach the controller. In preferred embodiments, the controller  160  is not attached to, and can be moved relative to, the levers of the upgrade device, allowing a user to completely let go of the levers to use the controller  160  to control the wheelchair speed and direction. In some applications, the controller  160  may be positioned on a handle of the wheelchair, or the controller  160  may be held by a person walking behind the chair, so that the person behind the chair can control operation of the device and movement of the chair. Alternatively, if capable, the person occupying the chair may hold and operate the controller  160 . 
     In some embodiments, the wheelchair upgrade system is configured with lightweight components so as to minimize the weight added to the receiving wheelchair. In preferred embodiments, the total weight of the upgrade system (including two upgrade devices—one on each side of the wheelchair) is less than about 40 pounds, less than about 30 pounds, or even less than about 20 pounds. For example, a presently preferred embodiment of a system with two upgrade devices has a weight of about 8 to 15 pounds (including battery, controllers, motors, housing, and power transmission components). Despite the relatively lightweight construction, the upgrade system is capable of propelling a wheelchair at over 5 miles per hour while supporting a user with a weight of about 200 pounds. 
     These low weight embodiments minimize any negative effects of integrating the upgrade system with a foldable wheelchair, and allow the upgraded wheelchair to maintain its previous benefits of being relatively lightweight and easy to move, store, transport, etcetera. Further, because the upgrade device  100  may function as a brake replacement, standard brake components are not necessary and may be removed, making the net weight gain from integrating the upgrade device  100  even lower. 
       FIG. 9  illustrates a wheelchair and attached wheelchair upgrade system in a folded position. As shown, the wheelchair may be folded without the need to detach or readjust the wheelchair upgrade system.  FIG. 9  also shows the importance of providing the upgrade devices in a size and attachment position that allows proper folding of the associated wheelchair. For example, the interior width of the device (the width of the portion of the device located interior to the frame when the device is attached; shown here by reference numeral  170 ) is preferably about 2 to 5 inches wide, or less than about 4 inches wide. The folded wheelchair can beneficially be placed in a standard car trunk, enabling storage and transport of the wheelchair without requiring removal of the upgrade system. 
     Although the foregoing has been described in some detail by way of illustrations and examples for purposes of clarity and understanding, it will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present disclosure. Therefore, it should be clearly understood that the forms disclosed herein are illustrative only and are not intended to limit the scope of the present disclosure, but rather to also cover all modification and alternatives coming with the true scope and spirit of the invention.