Abstract:
The wheelchair incorporates a telescoping pivoting input lever. At its lower end, the lever carries a footrest for securement to the user&#39;s feet. At its upper end, the lever is connected to a horizontal shaft rotatably mounted to the wheelchair frame, at an elevation below the top surface of the seat. The user pivots his lower legs about the knee joints to produce an oscillating pivoting motion. A drive assembly, incorporating the shaft, engages the lever with a rear wheel of the wheelchair. The drive assembly functions to convert the oscillating pivoting motion to forward rotational motion and to transmit this motion to the wheel to drive it. The telescopic nature of the lever enables the user&#39;s knees to remain stationary. Means are provided to regulate the length of the lever so that the footrest supports the lower legs. Means are also provided for manually engaging or disengaging the drive assembly so that the user can put the wheels into free-wheeling mode, when desired. The assembly is intended to enable the user to exercise the leg muscles in the course of propelling the wheelchair.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    Priority is claimed from U.S. Provisional Patent Application No. 60/265,687 filed Jan. 31, 2001, entitled “SYSTEM FOR USING LEG MOVEMENTS TO PROPEL A WHEELCHAIR,” which is incorporated by reference in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention relates to a wheelchair modified for propelling by a pivoting action of the user&#39;s lower legs about the knee joints.  
         BACKGROUND OF THE INVENTION  
         [0003]    Wheelchairs are commonly in use by people having weakness in their legs or balance problems. The present invention is concerned with providing a wheelchair which the user can propel by pivoting his lower legs about the knee joints, to thereby exercise his leg muscles.  
           [0004]    The conventional wheelchair comprises:  
           [0005]    a frame supporting a seat;  
           [0006]    a pair of free-wheeling large drive wheels rotatably mounted to the rear end of the frame;  
           [0007]    one or more free-wheeling, pivoting caster wheels mounted to the front end of the frame;  
           [0008]    a footrest extending down from the front of the frame, for supporting the lower legs; and  
           [0009]    circular push rims projecting outwardly from the rear wheels.  
           [0010]    The user grasps the push rims with his hands and propels the wheelchair forward or backwards using his arms and upper body. Pushing of the left and right push rims at different intensities or in different directions allows the chair to gradually turn or to “pivot on the spot”.  
           [0011]    Propelling the wheelchair with the hands, arms and upper body can lead to overuse injuries due to the somewhat unnatural movements performed in driving the push rims. In addition, the lower legs get no exercise and the leg muscles can atrophy. As a result, bones in the legs may become weaker and this can lead to fractures.  
           [0012]    A number of proposals have been made in the prior art with respect to modifying wheelchairs to address these problems.  
           [0013]    One approach involves providing levers to be pushed or pulled by the arms to power the wheels. The two-direction oscillation of the push and pull strokes is converted to rotational motion through a lever system and then converted to a unidirectional rotational motion through the use of a ratchet and pawl or one-way clutch system, to power one or both of the rear wheels. However this approach still relies on the upper body strength of the user to power the movement of the chair. U.S. Pat. No. 3,994,509, issued to Schaeffer, is an example.  
           [0014]    Other prior art devices have focussed on using the legs to power the chair. More particularly, U.S. Pat. No. 4,766,772, issued to Tsuchie, disclosed a pedaling assembly for rotating the wheels of a wheelchair. U.S. Pat. Nos. 4,421,336 issued to Petrofsky et al and 4,523,769, issued to Glaser et al, disclose an assembly utilizing back and forth sliding of the feet to propel the chair.  
           [0015]    U.S. Pat. No. 4,486,048, issued to Mayer, discloses a pivoting footrest. U.S. Pat. No. 5,033,793, issued to Quintile, shows a telescoping footrest. U.S. Pat. No. 4,586,723, issued to Nabinger, shows a steering caster assembly.  
         SUMMARY OF THE INVENTION  
         [0016]    It is an objective of the invention to modify a wheelchair so that pivoting of the user&#39;s lower legs about the knee joints, by extension and flexion of the knees, is used to propel the wheelchair.  
           [0017]    In a preferred embodiment, the invention comprises:  
           [0018]    a wheelchair having a frame, seat and front and rear wheels;  
           [0019]    a horizontal shaft rotatably mounted to the front end of the frame at an elevation below that of the top surface of the seat;  
           [0020]    a telescoping input lever connected at its upper end with the shaft and having a foot rest at its lower end, to which the user&#39;s feet are secured, whereby extension and flexion of the knees induces oscillating rotation of the shaft. The telescoping nature of the lever enables the axis of the knees to remain stationary, even though the pivot point of the lever is below that of the knee joints;  
           [0021]    means for controlling the extent of telescoping of the input lever so as to ensure that the foot rest supports or bears at least part of the load of the legs and the lever;  
           [0022]    drive assembly means, engaging the shaft with a rear wheel of the wheelchair, for converting the oscillating motion of the shaft into forward rotational motion and transmitting it to the wheel to drive it;  
           [0023]    means, controllable by the user, for selectively engaging or disengaging the drive assembly means so that the wheels can freely rotate; and  
           [0024]    means, manually controllable by the user, for steering at least one front caster wheel to control the direction of the wheelchair&#39;s forward movement.  
           [0025]    In one embodiment, there is provided a wheelchair having a frame pivotally connected with an input lever, preferably telescoping, that can be oscillated by extension and flexion of at least one of the user&#39;s knees. A drive assembly connects the input lever with a wheel of the wheelchair, for converting the oscillating motion of the lever into forward rotational motion and transmitting it to the wheel to drive it.  
           [0026]    To the best of my knowledge, it is novel to propel a wheeled frame using a lower leg, pivoting at the knee to actuate a pivoting input lever secured to the leg to thereby produce an oscillating pivoting motion that is then converted to a forward rotational motion which is transmitted to a drive wheel to move the assembly. This constitutes another embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0027]    [0027]FIG. 1 is an elevation of a wheelchair incorporation the invention and viewed from one side, with some parts removed for simplification;  
         [0028]    [0028]FIG. 2 is an elevation similar to that of FIG. 1, but viewed from the other side;  
         [0029]    [0029]FIG. 3 is a side elevation of the wheelchair with the input lever extended;  
         [0030]    [0030]FIG. 4 is a simplified side elevation showing the input lever, extension control assembly and part of the drive assembly, with an arrow identifying the rod which is active in the pull or contraction mode;  
         [0031]    [0031]FIG. 5 is a view similar to FIG. 4 with an arrow identifying the rod which is active in the push or extension mode;  
         [0032]    [0032]FIG. 6 is a simplified perspective view showing the input lever, frame, drive assembly and driven wheel, with the components in the contracted mode;  
         [0033]    [0033]FIG. 7 is a view similar to FIG. 6, showing the components in the extended mode;  
         [0034]    [0034]FIG. 8 is a partial side elevation, in section, showing the drive wheel and the engagement/disengagement portion of the drive assembly, in the clutch disengaged mode;  
         [0035]    [0035]FIG. 9 is an elevation similar to FIG. 8, in the clutch engaged mode;  
         [0036]    [0036]FIG. 10 is an exploded perspective view showing the engagement/disengagement portion of the drive assembly;  
         [0037]    [0037]FIGS. 11 and 12 are simplified side elevations of the assembly for engaging and disengaging the drive assembly;  
         [0038]    [0038]FIG. 13 is a side elevation of the wheelchair, showing the drive engagement assembly;  
         [0039]    [0039]FIG. 14 is an expanded simplified elevation of part of the wheelchair with parts removed;  
         [0040]    [0040]FIG. 15 is a front perspective view of the input lever;  
         [0041]    [0041]FIG. 16 is a simplified side elevation of the wheelchair showing the lever for controlling the brake band of the planetary gear assembly;  
         [0042]    [0042]FIG. 17 is a side elevation of the planetary gear assembly; and  
         [0043]    [0043]FIG. 18 is a side sectional elevation of the planetary gear assembly.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0044]    I have constructed the invention by starting with a commercially available wheelchair and modifying it. More particularly, I used a wheelchair I marketed under the trade-mark “ProSA” by Invacare Corporation, Elyria, Ohio. The wheelchair  1  comprises a frame  2  supported on rotatable rear wheels  3   a ,  3   b  and front caster wheels  4 . The frame  2  carries a seat  5  and backrest  6 . The rear wheels  3  have push rims  7  for manually propelling the wheelchair  1 .  
         [0045]    This wheelchair  1  has been modified in the following respects. A telescoping input lever  8 , having a footrest  9  at its lower end, is connected at its upper end with a horizontal shaft  10 . The shaft  10  is rotatably mounted to the front end of the frame  2 . An extension control assembly  11 , for regulating the extension and contraction of the input lever  8 , is connected between the frame  2  and the lever  8 . A drive assembly  12 , incorporating the rotatable shaft  10 , is connected between the input lever  8  and the axle shaft  13  of one of the rear wheels  3 . The drive assembly  12  functions to convert the oscillating pivoting movement of the input lever  8  into forward rotation of the driven rear wheel  3   a.  A drive engagement assembly  14  is provided for manually engaging or disengaging the drive assembly  12  with the driven rear wheel  3   a.  And a steering assembly  15  is provided to steer one of the front caster wheels  4 .  
         [0046]    In greater detail, the input lever  8  comprises inner and outer tubes  16 ,  17 . Linear ball bearings (not shown) are positioned in the annular space between the tubes  16 ,  17 . The bearings facilitate telescoping movement of the tubes  16 ,  17  between the contracted position shown in FIG. 4 and the extended position shown in FIG. 7.  
         [0047]    At its lower end, the input lever  8  carries a footrest  9 . The footrest  9  comprises a plate  20 , heel support  21  and toe strap  22 . I add pull straps  22   a , shown in FIG. 13, to combine with the heel support  21  and the toe strap  22  to firmly secure the user&#39;s feet to the plate  20 .  
         [0048]    At its upper end, the input lever  8  is connected to the horizontal shaft  10 . The shaft  10  is rotatably mounted to the frame  2 .  
         [0049]    The axis  23  of the shaft  10  is located at an elevation lower than that of the seat  5 . As shown in FIG. 3, the shaft axis  23  is also below and just behind the axis  25  of the user&#39;s knees. This positioning is used to ensure that there is no obstruction presented to interfere with the user moving sideways to leave the wheelchair.  
         [0050]    [0050]FIG. 3 illustrates the path  24  followed by the footrest  9  as it is moved between the contracted and extended positions. As the footrest  9  travels along the path  24 , the distance changes between the axis  23  of the shaft  10  and the footrest  9 . As a consequence the input lever  8  is made to be telescopic. Otherwise, the user&#39;s knees would be driven into his chest on the up stroke. By making the input lever  8  telescopic, the axis of the user&#39;s knees can remain stationary, which is desirable.  
         [0051]    The extension control assembly  11  is provided to ensure that the telescoping lever  8  and footrest  9  function to bear at least part of the weight of the user&#39;s legs and the lever.  
         [0052]    Having reference to FIGS.  1 - 5 , the extension control assembly  11  comprises a pulley support  30  attached to the shaft  10 . The pulley support  30  extends radially, rearwardly and generally horizontally from the shaft  10  when the input lever  8  is in the contracted or generally vertical position. The pulley support  30  carries a pair of pulleys  31 ,  32  spaced along its length. A cord  33  is attached at one end to the outer tube  17 . The cord  33  extends up the input lever  8  and passes over the pulleys  31 ,  32 . The other end of the cord  33  is secured to an anchor bar  34  which is fixed to the front end of the frame  3 . Thus the length of the cord  33  remains constant and its ends are fixed to the outer tube  17  and the frame  3 . As a result of this arrangement, when the leg muscles cause the input lever  8  to pivot upwardly, the pulley support  30  rotates downwardly, bringing the rear pulley  32  closer to the anchor bar  34 , This permits cord  33  to reel out from the front pulley  31  to enable the outer tube  17  to move along the inner tube  16 , thereby lengthening the input lever  8 . The weight of the user&#39;s feet on the footrest  9  keeps the cord  33  in tension as the input lever  8  extends and pivots upwardly. When the user&#39;s leg muscles flex the knees and cause the upraised input lever  8  to pivot downwardly from the raised position, the outer end of the cord  33  is reeled in as the rear pulley  32  moves away from the anchor bar  34 . The inwardly reeling cord  32  pulls the outer tube  17  along the inner tube  8  and the input lever  8  contracts accordingly.  
         [0053]    As shown in FIGS. 5,6 the anchor bar  34  is connected with the frame  3  by ears. Support  35  has a series of spaced apart holes  36  extending therethrough along its length. Anchor bar  34   a  extends into a selected pair of aligned holes  36 . The position of the anchor bar  34   a  therefore can be adjusted by moving it from one pair of holes  36  to another. By making this adjustment, the length of the input lever  8  in the contracted state can be varied to match the length of the user&#39;s lower legs.  
         [0054]    As a consequence of providing this construction, the axis of the user&#39;s knees (the position of which is indicated by the “+” on FIG. 3) remain stationary, while the lower legs pivot with the feet locked to the footrest  9 .  
         [0055]    As previously stated, a drive assembly  12  engages or drivably connects the input lever  8  with the driven rear wheel  3   a . This drive assembly  12  comprises: the rotatable shaft  10 ; crank arms  40 ,  41  connected with the shaft  10 ; pull and push rods  43 ,  42  pivotally connected at their front ends with the crank arms  40 ,  41 , respectively; a one-way pull clutch  45  connected with the rear end of the pull rod  43 ; a one-way push clutch  44  connected with the rear end of the push rod  42 ; the clutches  44 ,  45  being operatively connected with a large sprocket  46 ; the clutches  44 ,  45  each being adapted to engage and rotate the sprocket  46  through an angular travel when drive force is being applied by the input lever  8  to their associated rod  42  or  43 ; the large sprocket  46  driving a small sprocket  47  through a chain  48 , whereby one rotation of the large sprocket  46  induces several rotations of the small sprocket  47 , for example to provide an input/output ratio of 1:3; the small sprocket  47  being operative to engage and transmit its rotational motion to the driven rear wheel  3   a  when actuated by the drive engagement assembly  14 . I refer to the assembly between the clutches  44 ,  45  and the driven wheel  3   a  as the transmission assembly  100 . It functions to amplify the rotational speed of the input to the output and selectively transmits the output to the driven wheel.  
         [0056]    The drive assembly  12  functions to convert the oscillating pivoting motion of the input lever  8  into forward rotational motion which is transmitted to the rear drive wheel  3   a.    
         [0057]    More particularly, the pull and push crank arms  40 ,  41  are affixed to the shaft  10  and extend radially therefrom at different angles. As shown in FIG. 14, each of the crank arms  40 ,  41  forms a series of spaced apart adjustment holes  49  along its length. The forward ends of the pull and push rods  43 ,  42  are pivotally connected with their respective crank arms  40 ,  41  by pins  50  extending through holes  49 . At their respective rear ends, the rods  42 ,  43  are pivotally connected by pins  51  with the arms  52 ,  53  of one-way clutches  44 ,  45 , respectively. I use one-way clutches available, under the designation KK-30, from Morse and Sealmaster, Florence, Ky. The clutches  44 ,  45  are each press-fitted onto the hub  54  of a large drive sprocket  46 . The hub  54  is rotatively mounted to the frame  3  by ears  54   a  and  54   b.    
         [0058]    In operation, when the input lever  8  is raised on the pivoting upstroke, as shown in FIG. 5, the pull crank  40  pulls on the pull rod  43  and rotates the arm  53  of the pull clutch  45 , thereby forwardly rotating the hub  54  and drive sprocket  46  through an angular travel. These actions are indicated by the arrows on FIG. 5. When the input lever  8  is lowered on the pivoting downstroke, as shown in FIG. 4, the push crank  41  pushes on the push rod  42  and rotates the arm  52  of the push clutch  44 , thereby also forwardly rotating the hub  54  and drive sprocket  46  through a further angular travel. When one clutch is so engaged, the other clutch slips.  
         [0059]    The drive sprocket  46  is connected by a chain  48  with the small driven sprocket  47 .  
         [0060]    Turning now to FIGS. 8, 9 and  10 , there is shown my first conceived transmission assembly  100 . It comprises:  
         [0061]    a wheel hub  60  which supports the spokes  61  and tire  62  of the driven rear wheel  3   a;    
         [0062]    an anchor shaft  63  which supports the wheel hub  60  and the tubular driven axle  64 ;  
         [0063]    the wheel hub  60  forming axial pin holes  65 ;  
         [0064]    the driven axle  64  having axial drive pins  66  received in the pin holes  65 , so that the driven axle  64  and wheel hub  60  are engaged for rotation together;  
         [0065]    the anchor shaft  63  containing lock balls  67  which engage recesses  68  formed by the bore surface  69  of the driven axle  64 , to disengagably hold the anchor shaft  63  and driven axle  64  together;  
         [0066]    a stationary annular bearing holder  69   a  which is bolted to the frame  2  and carries bearings  70  which support and facilitate rotation of the driven axle  64 ;  
         [0067]    a stationary bolt sleeve  71  forming a threaded hole  72  for receiving an engagement/disengagement (“E/D”) bolt  73 , the bolt sleeve  71  being bolted to the bearing holder  69   a;    
         [0068]    a slot sleeve  74  forming a helical slot  75 . The slot sleeve  74  extends around and is slideable along the bolt sleeve  71 . The E/D bolt  73  extends through the slot  75  and threadably engages the hole  72  in the bolt sleeve  71 . Consequently, when the slot sleeve  74  is rotated, the interaction of the E/D bolt  73  and slot wall  76  causes the slot sleeve  74  to move axially, in or out;  
         [0069]    the end of the driven axle  64  rotatably supporting a tubular one-way overrun clutch  78  which has a portion  79  internal of the bolt sleeve  71  and a portion  80  external of the bolt sleeve  71 . The exterior portion  80  forms external splines  81  and a non-splined release groove  82 . The one-way overrun clutch can drivably engage the driven axle  64 , when actuated. I use an overrun clutch  78  which is a commercial product available under the designation “Roller Clutch Freehub Body” from Shimano American Corporation, Irvine, Calif.;  
         [0070]    the small sprocket  47 , which has internal teeth  83 , is mounted around the overrun clutch  78 . The sprocket  47  can be shifted axially, by rotation of the slot sleeve  74 , between the release groove  82  and the splines  81  of the overrun clutch  78 . An assembly  84  of inner and outer rings  85 ,  86  and coil spring  87 , mounted around the external portion  80 , functions to normally urge the sprocket  47  away from the release groove  82 . A lock ring  88  retains the assembly  84  on the exterior portion  80 ; and  
         [0071]    a manually operated lever  89  is connected with the slot sleeve  74 , for rotating the latter to shift the sprocket  47  from the release groove  82  and into engagement with the splines  81 .  
         [0072]    When the small sprocket  47  is positioned in the release groove  82 , the wheel  3   a  and driven axle  64  can freely rotate in either direction. The overrun clutch  78  is actuated by shifting the small sprocket  47  into engagement with the splines  81 . When this occurs, the driven wheel  3   a  and the driven axle  64  can overrun or freely rotate forwardly, independent of the sprocket  47 , until the sprocket  47  is driven at a rotational speed greater than that of the driven axle  64 . At that point, the sprocket  47 , the overrun clutch  78  and driven axle  64  lock up or engage together and rotate forwardly under the impetus of leg action.  
         [0073]    Thus the user can engage the sprocket  47  and overrun clutch  78  by moving the lever  89 , then rotate the wheels  3   a ,  3   b  forwardly using the push rims  7  while simultaneously pivoting the lower legs until lock up occurs, following which leg action drives the driven wheel  3   a . To facilitate reverse movements of the push rims  7 , the lever  89  is shifted, thus positioning the sprocket  47  over release groove  82 , thereby enabling free rearward movement of wheel  3   a.    
         [0074]    FIGS.  16 - 18  show an alternative later and simpler version of the transmission assembly  100 . This later version utilizes a modified planetary gear assembly of otherwise conventional design. I use a planetary gear assembly available from Matex Products Corporation, Cleveland, Ohio, under designation 3MHN. More particularly, this transmission assembly  100  comprises:  
         [0075]    an input shaft  101  coupled to the one-way clutches  44 ,  45  and to a planet carrier  102  carrying rotatable planet gears  103 ;  
         [0076]    a ring gear  104  meshing internally with the planet gears  103  and having a smooth external circumferential surface  105 ;  
         [0077]    a central sun gear  106  meshing with and driven by the planet gears  103 , the sun gear  106  being coupled with the driven output axle  13  driving the wheel hub  60 ;  
         [0078]    a brake band  107  for disengagably and frictionally engaging the external surface  105  of the ring gear  104 ;  
         [0079]    a lever and cam assembly  107   a  for controlling the brake band  107 ; and  
         [0080]    a housing  108  containing the gear set and supporting the input shaft  101 , lever and cam assembly  107   a  and output axle  13 , all with bearings  109 ,  110  respectively.  
         [0081]    As a result of this construction, the brake band  107  may be clamped to immobilize the ring gear  104 , thereby enabling the rotational input of the input shaft  101  to be transmitted through the gears to the output axle  13  and wheel  3   a . In this mode (used when the lower legs are in action), the wheels  3   a ,  3   b  cannot be backed up. Alternatively, the brake band  106  may be unclamped, thereby allowing the ring gear  104  to slip and disengaging the wheel  3   a  from the input shaft  101  and placing it in a free-wheeling condition in either direction.