Abstract:
A power drive apparatus is easily attachable to a conventional wheelchair for converting it into a powered wheelchair. The only change to the conventional wheelchair is the addition of a pair of mounting studs clamped to the front of the wheelchair. The power drive apparatus has an adjustable frame to adapt it to a range of wheelchair configurations and includes a novel mount for the drive motor. A severe-off-road-use version is shown which includes a separate, inboard, non-road-contacting ring for maintaining good driving and braking performance under adverse environmental conditions.

Description:
BACKGROUND OF THE INVENTION AND PRIOR ART  
       [0001]    This invention relates generally to wheelchairs and specifically to wheelchairs that are lightweight, manually operable and readably transportable. 
         [0002]    Manually operable, i.e., hand propelled, wheelchairs have been manufactured for more than a century without significant change. Generally hand rings are mounted on large drive wheels to assist in propulsion by the user, although very often the actual tires are gripped by the user to propel the wheelchair. Such wheelchairs are generally satisfactory for indoor use over fairly short distances where floors are usually flat and smooth. Outdoor operation on the other hand, on soft ground and up and down hills, presents challenging obstacles for a user of a hand propelled wheelchair. Therefore, some sort of powered wheelchair is very desirable for outdoor use. 
         [0003]    Most powered wheelchairs and powered scooters are heavy, complicated, expensive machines. They have small, fat tires and fairly complex joy stick-operated control systems. They generally include two electric motors that may be driven by one or more large lead-acid batteries. While intended for outdoor as well as indoor use, the machines are ill-suited for unpaved surfaces like grass and dirt. Nonetheless, powered wheelchairs and scooters have been a boon to the handicapped and elderly. 
         [0004]    Scooters generally have a single motor that drives the wheels through a differential. While the costs and weight of a differential are about the same as an extra motor and gear reduction mechanism, the controls on the scooter are less complicated and the unit is generally more reliable than a two-motor wheelchair. Steering of the front wheel of the scooter is accomplished with a small handlebar. The shopping cart is the most popular type powered scooter and, while designed primarily for indoor use, it also sees limited outdoor service in transporting both the user and groceries across the store parking lot. These vehicles&#39; major drawbacks of cost, bulk and weight (generally in the range of 150 to 200 pounds), have prevented their widespread acceptance despite their obvious advantages. They also require special measures in order to transport them. A serious drawback is that the motor drives the wheels through gearing which cannot be overdriven. Thus a drive failure, or a dead battery, can leave the 200 pound vehicle frozen in place with its wheels effectively locked and the user helplessly stranded. 
         [0005]    Generally a special type van, or other vehicle providing a large door opening and specialized access equipment, is required to transport powered wheelchairs and powered scooters. The expensive vehicle is usually equipped with a power lift of some sort to enable loading and unloading of such a wheelchair. 
         [0006]    The present invention is specifically directed to wheelchairs that are lightweight, compact and maneuverable and which are designed to have great appeal to persons of limited disability who wish to project a more able and athletic persona. Such wheelchairs are available in very light weight materials such as titanium and often have carbon fiber wheels and customized paint schemes to reflect a more active lifestyle. Despite the light weight and maneuverability of these manual wheelchairs, powered wheelchairs are far more capable of handling hills, grass and off road conditions. Thus, Applicants&#39; perceived a need for some means to enable light weight wheelchairs to be motorized, preferably without detracting from the appearance, maneuverability and transportability of the wheelchair. 
         [0007]    Applicant&#39;s U.S. Pat. No. 6,273,212, issued Aug. 14, 2001 describes a lightweight maneuverable power chair that uses a drive system that is similar to that of the present invention. The power chair of the patent is especially suitable for longer distances and outdoor use over difficult terrain, and may be readily transported without the need for special equipment. 
         [0008]    Applicants&#39; U.S. Pat. No. 6,371,228, issued Apr. 16, 2002 describes a stable, low speed powered tricycle with a traction steering drive system similar to that of the present invention. A version of the tricycle that has many recreational uses is also disclosed in the patent. 
         [0009]    As mentioned above, the power chair of the invention is readily transportable in the trunk of a compact automobile and is easily hand propelled, when indoors, because of its lack of bulk and extreme light weight. It has in addition, excellent maneuverability and its drive wheels are normally free wheeling. Propulsion and steering are provided by selectively engaging the drive wheels with friction drive rollers that are affixed to the axle of a DC motor. The engagement between the friction rollers and the drive wheels is controlled by a pair of rocker levers that are simultaneously pushed forward for forward propulsion and pulled backward for braking. Normal turning is accomplished by engaging only one of the friction rollers with the desired drive wheel. Very tight turns may be made by simultaneously engaging the friction roller corresponding to the desired drive wheel and the opposite brake surface with the other drive wheel. 
       OBJECTS OF THE INVENTION 
       [0010]    A principal object of the invention is to provide a novel wheelchair. 
         [0011]    Another object of the invention is to provide a novel powered wheelchair that is lightweight, maneuverable and easily transportable. 
         [0012]    A feature of the invention resides in the arrangement for rapidly converting a manual wheelchair into a powered wheelchair. 
         [0013]    Another feature of the invention resides in a motor mount that permits limited rotational, pivotal and translational movements. 
         [0014]    A still further feature of the invention resides in the adjustable frame for enabling the invention to be adapted to a range of wheelchair dimensions. 
         [0015]    Still another feature of the invention resides in a special tire and drive arrangement for enabling heavier off road use. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    These and other objects and features of the invention will be apparent upon reading the following description in conjunction with the drawings in which: 
           [0017]      FIG. 1  shows a prior art lightweight wheelchair; 
           [0018]      FIG. 2  is a side view of the inventive power drive apparatus; 
           [0019]      FIG. 3  is a side view of the prior art wheelchair of  FIG. 1  with the invention of  FIG. 2  installed; 
           [0020]      FIGS. 3A and 3B  illustrate clamps used with the invention; 
           [0021]      FIG. 4  is a front view of the wheelchair of  FIG. 3  with a portion of the left side cut away; 
           [0022]      FIG. 5  is a front view of the power drive apparatus of the invention; 
           [0023]      FIG. 6  is a top view of the power drive apparatus of the invention; 
           [0024]      FIG. 7  is an enlarged partial view taken along the line  7 - 7  of  FIG. 5  showing the novel motor suspension system of the invention; and 
           [0025]      FIGS. 8 and 9  illustrate the invention for use with a wheelchair having knobby tires for more rugged off-road use. 
       
    
    
     SUMMARY OF THE INVENTION 
       [0026]    The invention comprises a power drive apparatus that may be quickly and easily installed on a manually operable wheelchair to convert it into a motorized wheelchair. It includes a battery; a motor and control system; brake surfaces or pads; friction drive rollers connected to the motor; and user operated rocker levers, for selectively engaging the drive rollers and/or brake surfaces with the wheelchair drive wheels for propelling, turning and braking the wheelchair. The power drive apparatus frame is adjustable to adapt to a range of wheelchair dimensions. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]      FIG. 1  illustrates a prior art lightweight, wheelchair  10  having a frame  12  supporting a seat  14  and includes a pair of free wheeling drive wheels  16  and a pair of front caster wheels  18 . The drive wheels are equipped with rubber tires, and smaller hand rings, to facilitate user propulsion. Since these lightweight wheelchairs are designed for portability, they generally include mechanisms that permit rapid removal and replacement of the drive wheels to facilitate storage in automobile trunks and the like. It will be appreciated that such wheelchairs are well known in the art and form no part of the present invention. 
         [0028]      FIG. 2  is a side view of the power drive apparatus  20  of the invention which is adapted to be rapidly secured to (and removed from) the wheelchair of  FIG. 1 . The wheelchair and the power drive apparatus generally have left and right side symmetry; for simplicity therefore, the discussion will reference the right sides. As most clearly shown in  FIGS. 5 and 6 , power drive apparatus  20  comprises a generally H-shaped frame formed by a pair of parallel tubular side members, each consisting of a center section  22 , a telescoping rear section  24  and a telescoping front section  26 , joined by cross members  37  and  39  having telescoping end pieces  37   a  and  39   a,  respectively. It should be noted that cross member  37  defines a common axis for the power drive apparatus. Front section  26  terminates in a slotted end bracket  28  and rear section  24  is fitted with an anti tip wheel  30 . The ends of center sections  22  and cross members  37  and  39  are split and, in cooperation with four double-tube clamping blocks  42 , enable the distances A, B, C and D to be changed to adjust power drive apparatus  20  to wheelchairs of slightly differing dimensions. The double-tube clamping blocks secure tubular members crossing at right angles and enable movement of the telescoping members to adjust the frame. Once the power drive apparatus is set up for a particular wheelchair, its configuration is secured by tightening bolts in clamping blocks  42 . 
         [0029]    A rocker lever  34  has a twist grip  36 , which houses a throttling device or other well-known adjustment device (not shown) at one end, terminates in a rotatable sleeve  55 . (It will be appreciated that a similar rocker lever  34   a,  with a grip  36   a,  on the opposite side of the frame also terminates in a rotatable sleeve  55   a  and that both rotatable sleeves are on the common axis. However, grip  36   a  does not rotate and does not contain a throttling device.) A bearing bracket  54  extends downwardly from sleeve  55  and supports one end of an axle  51  of a DC motor  40 . A resiliently mounted ball bearing, not shown, is secured in the end of bearing bracket  54 , the resilient mounting permitting limited movement of the ball bearing to accommodate angular variations of the motor axle  51  responsive to rocker lever movement. A drive roller  52  is secured to the end of axle  51  and a brake pad  38  is welded to rocker lever  34 . A power system box  50  is secured to cross member  39  and includes a battery and a suitable electronic speed controller (neither shown) for supplying a variable DC voltage to motor  40 , via wiring  57 , responsive to rotation of twist grip  36 . A bracket  32 , as will be seen, includes a hole  46  for suspending power drive apparatus  20  from the axle-supporting support structure  33  of the wheelchair. 
         [0030]      FIGS. 3 and 4 , respectively, show the side and front views of wheelchair  10  fitted with power drive apparatus  20 . The only additions required for wheelchair  10  are front clamps  80  to which the slotted end brackets  28  are secured. As shown in  FIGS. 3A and 3B , front clamp  80  comprises a split collar, secured via bolts  82  to frame  12 , which supports a stud  84  for securing end bracket  28  thereto via a large wing nut  86 , or other suitable attachment device. 
         [0031]    Drive roller  52  and brake pad  38  are normally positioned close to, but out of contact with, the periphery of drive wheel  16 . Thus, with no force applied to twist grip  36  (and its corresponding grip on the other side of the wheelchair) the wheelchair is “free wheeling” and may be operated manually. Pushing forward on twist grip  36  rotates sleeve  55  to engage drive roller  52  with wheel  16 , whereas pulling backward on twist grip  36  engages brake pad  38  with wheel  16 . 
         [0032]    In  FIG. 4  motor  40  is seen to be supported from cross tube  37  by a special mount  70  that is described in detail below. As mentioned above, the sleeves  55 , with bearing brackets  54 , are journaled for independent rotational movement on opposite ends of cross tube  37  about the common axis. In this manner sleeves  55  are independently movable by the rocker levers to cause selective engagement between the drive rollers, brake pads and drive wheels. As shown, drive wheel  16  has a short axle  15  that fits within support structure  33 . As mentioned above, drive wheel  16  is preferably secured to the wheelchair by a quick release mechanism. 
         [0033]    In  FIG. 7  a sleeve bushing  72  is rotatably mounted on cross tube  37 . A collar  74  is welded to sleeve bushing  72  and supports a bushing  76  therein. Bushing  76  may be made of rubber, although that is not required. A stud  78  is welded to motor  40 , extends through bushing  76  and has a nut and washer  80  secured to its threaded end. The arrangement enables the weight of motor  40  to be supported by collar  74  while being capable of; rotational movement about sleeve bushing  72 ; rotational movement within collar  74 ; and translational movement within collar  74 . These movements are indicated by the arrows E, F and G which result from user operation of the rocker levers for propelling, steering and braking of the wheelchair. It will be noted that for forward movement or braking, the rocker levers rotate about the common axis and there is no tendency for translational movement (arrow G) of the motor in the collar. For opposed rocker lever movements, the motor is moved in the direction of arrow G. 
         [0034]      FIGS. 8 and 9  depict a modified wheel for use with the invention in conditions where water, mud, road debris and the like are expected to be encountered. The modified wheel includes a large, knobby tire  17  for greater traction under such conditions and a smaller diameter inboard-mounted ring  19  having a friction surface for engagement with the drive roller and brake pad. The knobby tire, while excellent for enhanced traction, does not mate as well with the drive roller and brake surface of the power drive apparatus. The added inboard ring, on the other hand, being of smaller diameter than the knobby tire, remains relatively free of water, mud and road debris and continues to interface well with the drive roller and brake surface. Ring  19  is secured to the wheel by means of a plurality of brackets  21 . It will be appreciated that the frame of the power drive apparatus will be adjusted to conform to the new dimensions imposed by the added inboard ring  19 . 
         [0035]    What has been described is a novel power drive apparatus for attachment to a conventional wheelchair to convert it into a powered wheelchair. The power drive apparatus has an adjustable frame to adapt it to a range of wheelchair configurations and includes a novel suspension system for the drive motor.