Abstract:
A balance tool for evaluating weight distribution of a wheelchair positioned on an elongated platform with a support extending from a lower surface and a linear scale, a measuring bar slideably movable relative to the linear scale for making measurements of horizontal distances between a center of mass and the center of the front wheels and the rear wheels, for determining the relative weight carried by the wheels and for adjusting the position of the wheels to have the rear wheels carry a substantial majority of the weight. A method of adjusting the balance of a wheelchair is disclosed.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to tools for configuring a wheelchair. More particularly, the present invention relates to a balance for determining weight distribution in order to configure a wheelchair for a user. 
       BACKGROUND OF THE INVENTION 
       [0002]    Wheelchairs are mobility devices by which a person who is unable to walk can move while engaging in ordinary life activities. Wheelchairs typically have a seat and back attached to a chassis or frame. A pair of drive wheels attach to opposing sides of the frame. A pair of caster wheels mount to opposing forward portions of the frame. Accessory devices including lateral side supports, pads, and cushions, attach to the frame or seating structure for supporting an individual occupying the seat. Anti-tip arms typically extend rearwardly from the frame close to a surface over which the wheelchair moves. The anti-tip arms restrict the wheelchair from tipping over backwards. 
         [0003]    The anti-tip arms are particularly useful because the wheelchair typically is configured so that a substantial majority of the weight distribution is carried rearwardly on the wheelchair. This makes the front portion of the wheelchair relatively light and the chair is “tippy”. The anti-tip arms restrict the wheelchair from tipping over backwards. This weight distribution however is beneficial to facilitate the driving operation of the wheelchair by the user. The front end rolls on the surface but is relatively easier to move over surface obstructions such as grass, gravel, curbing, transitions between floor surfaces, rugs and the like. In some instances, the user of the wheelchair preferably elevates the front end so there is less rolling resistance to facilitate movement of the wheelchair. 
         [0004]    Wheelchair weight balance distribution can be manually accomplished by repeated configuration and test rolling by the user of the wheelchair. This however is time consuming and may not be entirely satisfactory as the test rolling of a particular configuration may not test the particular situations that the user faces, and subsequent reconfiguration is needed. 
         [0005]    Accordingly, there is a need in the art for a tool for evaluation of the weight distribution of wheelchairs. It is to such that the present invention is directed. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The present invention meets the needs in the art by providing a balance tool for evaluating weight distribution of a wheelchair, comprising a platform having a support that extends from a lower surface thereof and a linear scale attached to the platform and extending longitudinally relative to the platform. A guide slideably attaches to the platform and an indicator extends perpendicularly therefrom, the guide movable relative to the linear scale for aligning the indicator in order to make measurements of horizontal distances between a center of gravity of a wheelchair and occupant positioned on the platform and the center of the front wheels and of the rear wheels of the wheelchair. 
         [0007]    In another aspect, the present invention provides a method of balancing weight distribution of a wheelchair, comprising the steps of: 
         [0008]    (a) positioning a wheelchair on a platform having a planar surface and opposing upstanding side walls, the platform including a support that extends from a lower surface thereof intermediate opposing longitudinal ends of the platform, the wheelchair moved thereon to align the center of gravity in alignment with the support; 
         [0009]    (b) moving an indicator longitudinally relative to the support to align selectively with a center of a front wheel and with a center of a rear wheel; 
         [0010]    (c) measuring the horizontal distance between the support and the selected front wheel and rear wheel; 
         [0011]    (d) determining the distribution of weight on the front and rear wheels; 
         [0012]    (e) adjusting the position of rear wheel relative to the front wheel to position a substantial majority of the weight on the rear wheels. 
         [0013]    Objects, advantages, and features of the present invention will become apparent upon a reading of the following detail description in conjunction with the drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of the balance tool in accordance with the present invention. 
           [0015]      FIG. 2  is a detailed side view of a slidable guide and indicator used with the balance tool shown in  FIG. 1 . 
           [0016]      FIG. 3  illustrates in perspective view the balance tool shown in  FIG. 1  being used for determining the weight distribution for a wheelchair. 
           [0017]      FIG. 4  is a detailed partially cut-away side view of an alternate embodiment of the guide and indicator used with the balance tool shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    With reference to the drawings, in which like identifiers have like reference numerals,  FIG. 1  illustrates in perspective view a balancing tool  10  for determining weight distribution during configuration of a wheelchair for a user. The balance tool  10  includes a pair of spaced-apart platforms  12 . The platforms  12  receive the spaced-apart wheels of a wheelchair to be evaluated, as discussed below. An alternate embodiment (not illustrated) uses a single platform sized for receiving a wheelchair. A fulcrum  14  extends from a lower surface of the platform  12 . The fulcrum  14  is aligned with a transverse axis medial opposing longitudinally spaced edges  18  of the platform  12 . 
         [0019]    In the illustrated embodiment, the fulcrum  14  comprises an elongated support  20  mounted to a lower surface of the platform and an elongated tube  22 . The support  20  defines a channel  23 . The channel  23  aligns with the transverse axis  16  of the platform  12 . The channels  23  of the spaced-apart platforms  12  receive the elongated tube  22 . The tube  22  in the illustrated embodiment is a one-inch diameter tube. 
         [0020]    The platforms  12  are U-shaped in cross-sectional view with a planar surface  24  and a pair of opposing upstanding sidewalls  25 . A scale  26  attaches to an outside face of one of the opposing sidewalls  24 . The scale  26  includes a graduation of intervals with a plurality of uniformly spaced demarcations  28  and associated numerical indicia  30 . In the illustrated embodiment, the scale  26  centers at a zero (“0”) value along the transverse axis  16 . The indicia  30  increment sequentially unitarily in opposing directions from the scale mid-point to the edges  18 . For example, in one embodiment, the scale  26  centers at zero “0” and includes ruler graduations of inches, half inches, quarter inches, and eighth inches, for measuring purposes, with the numerical indicia associated with the inch graduation marks. 
         [0021]    In the illustrated embodiment, the platforms  12  include feet  32  extending from a lower surface at the edges  18  of the platform  12 . The feet  32  extend to a distal edge. The distance is in a range of between about ¼ to ½ inch. The tube  22  however extends further from the platform  12 . This leaves a gap between a distal edge of the feet  32  and a surface on which the fulcrum  14  sits. The platforms  12  accordingly can pivot on the fulcrum  14  so that one edge  18  of the platform is elevated and the opposing edge is lowered. 
         [0022]    A guide or slider  36  slidingly attaches to the platform  12 . In the illustrated embodiment, the slider  36  slidably attaches to the one of the side walls  25  having the scale  26 . In an alternate embodiment (not illustrated) the slider seats on the support surface of the platform aligned with the scale  26 . The slider  36  includes an indicator for aligning with selected portions of the wheelchair such as a central hub of the wheel for taking horizontal measurements as discussed below. In the illustrated embodiment, the indicator is an elongated arm  38  and the body of the slider defines a support  40  attached to a side of the arm near a first end. The arm  38  extends upwardly from the platform  12 . 
         [0023]    As illustrated in exploded view in  FIG. 2 , the support  40  defines a notch  42  with a first sliding face  44  that moves on a distal edge  43  of the side wall  25  and a second sliding face  46  that moves on an inner side face  48  of the side wall  25 . Fasteners such as screws or rivets secure the arm  38  to the support  40 . The support  40  and the arm  38  cooperatively define a gap  50  for receiving the side wall  25 . 
         [0024]      FIG. 3  illustrates the balancing tool  10  in use during weight distribution determination for configuration of a wheelchair  52 . The balancing tool  10  readily assembles by placing the tube  22  on a surface such as a floor. The platforms are positioned in spaced-apart relation on the tube  22  with the channels  23  of the supports  22  receiving a portion of the tube  22 . The platforms  12  are tilted by pivoting on the tube  22  so one end  18  is lowered to the surface on which the tube  22  sits. The wheelchair  52  is occupied by the user (partially illustrated), who rolls the wheelchair onto the platforms  12 . 
         [0025]    The wheelchair is then positioned so that the center of gravity of the user and the wheelchair is directly above the fulcrum  14 . The center of gravity of the wheelchair and occupant is the point through which the resultant of gravitational forces on the user and the wheelchair passes and is coincident with the center of mass in a uniform gravitational field. The positioning of the wheelchair is accomplished by moving the wheelchair longitudinally relative to the platform  12  between the opposing ends  18  and observing that the platforms  20  are relatively balanced in side view (the platform  12  is approximately level). 
         [0026]    A physical therapist or other individual configuring the wheelchairs (partially illustrated) moves the slider  26  longitudinally to align an edge of the arm  38  with a center or hub of the front wheel  54 . The edge of the arm  38  indicates on the scale  26  the distance from the center of gravity of the occupied wheelchair  30 . The horizontal distance from the fulcrum  14  to the center of hub of the rear drive wheels  56  is also measured. 
         [0027]    The distances are used to calculate the percent of weight on the front and rear wheels. This determination gives a measure of the stability of the wheelchair occupied by the user. Preferably, the wheelchair is configured with a substantial majority of the weight towards the rear. Typically, 70 to 95% of the weight is carried on the rear wheels. 
         [0028]      FIG. 3  illustrates in partially cut-away side view an alternate embodiment of the balancing tool  10 . A light-emitting device  60  installs in the support  40 . The device  60  emits a narrow focused beam  66 , such as a laser-emitting device and eliminates the portion of the vertical arm  38  that extends from the support in a direction away from the platform  12 . Laser devices are conventional and operate on batteries. The support  40  in this embodiment includes a window  62  through which the beam  66  emits and a battery compartment selectively openable (not illustrated) for replacing batteries from time-to-time. An on-off switch  64  communicates electrically between the batteries and the device  60  to control selectively the emission of the laser light. 
         [0029]    The support  40  with the lower portion of the member  38  slidably engages the scale  26 . The light emitting device  60  emits the narrow beam  66  through the window  62  away from the platform  12  upwardly towards the wheelchair. The light is projected onto the wheelchair, and the support  40  moved slidingly to align with the center of the wheel hub. The scale  26  is then read relative to the slide  40  for determining the horizontal distance measurements. The use of the laser light device reduces potential errors in measurement that may arise from looking at the vertical guide or member  38  at an angle. 
         [0030]    In response to the determination of weight distribution, the wheelchair stability can be adjusted. This is accomplished by moving the axle of the drive wheels longitudinally relative to the frame of the wheelchair. A properly balanced wheelchair facilitates the user of the wheelchair moving the wheelchair, for example, across grass, roads, curbs, carpeting, and the like. A properly balanced wheelchair also facilitates moving the wheelchair downhill. Often wheelchair users will cause the front end of the wheelchair to elevate. This is accomplished by the user sitting back in the wheelchair and forcing the front of the wheelchair to elevate. This provides more comfortable seating as the user is not leaning forward. The anti-tip members extending from the rear of the wheelchair prevent the wheelchair from tipping over. 
         [0031]    The wheelchair balance tool and method disclosed herein can be made and executed without undue experimentation in light of the present disclosure. While the apparatus and methods of this invention have been described in terms of illustrative embodiments, it will be apparent to those of skill in the art that variations may be applied to the apparatus and in the method steps or in the sequence of steps thereof described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.