Abstract:
A wheelchair includes a standard foldable frame for supporting a seat with a first and second drive wheel driven by drive levers. Each wheel has a transmission providing for three forward speeds and a reverse speed, as well as a neutral position. The transmissions for the two wheels may be constructed of identical parts with the wheels being caused to rotate in opposite directions from the driving lever merely by reversing the direction of the pawls within the transmissions. The ratchet drive surfaces are provided with pawl engaging surfaces which may be driven in either of two directions. The wheelchair does not require any bulky equipment and the hub containing the transmission may be the size of a bicycle hub. The transmissions in both wheels are shifted by a single control. The wheelchair is provided with disk brakes.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a manually driven wheelchair. More particularly, the present invention relates to a manually driven wheelchair which is foldable and may be driven by levers in a forward direction in a first, second and third (or more) speed, as well as in a reverse direction, and is provided with a neutral or freewheeling condition and disk brakes. 
       BACKGROUND OF THE INVENTION 
       [0002]    Much work has been done in the field of wheelchairs. However, there is still a need for a wheelchair which may be conveniently powered by a manual means other than the user&#39;s hands directly on the wheels of the wheelchair. There is also a need for a wheelchair which may be substantially similar to foldable wheelchairs which may be conveniently folded for transport of the wheelchair in a vehicle or the like and readily unfolded for use. 
         [0003]    Further, there is a need for a wheelchair which does not comprise bulky components which detract from the useability of the wheelchair. 
         [0004]    There is also a need for a wheelchair which may be driven in a forward direction in multiple speeds or powered torque levels. There is further a need for a wheelchair which may be driven in forward or reverse or in which either one or both of the wheels may be easily put into a neutral or freewheeling condition. 
         [0005]    Further, there is a need for a wheelchair which may be economically manufactured. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides or satisfies the needs in the field of wheelchairs as set forth above. 
         [0007]    An advantage of the present invention is that it provides a wheelchair which may be manually driven by a pair of levers, one for each wheel, without the user having to handle or place his or her hands directly on the driving wheels. 
         [0008]    Another advantage of the present invention is that the wheelchair of the present invention remains foldable for storage or transport and may be readily unfolded for use. 
         [0009]    Another advantage of the present invention is that it provides two, three or more speeds of forward motion or two, three or more speeds of torque power which may be easily selected by a thumb operated selector on one of the levers. 
         [0010]    Another advantage of the present invention is that it provides a manually lever powered multi-speed forward and a reverse manually lever powered drive, as well as a neutral or freewheeling condition for both wheels. 
         [0011]    Another advantage of the present invention is that by selecting on a single speed selector on one of the levers, both transmissions are automatically set to the same transmission speed. 
         [0012]    Another advantage of the present invention is that each wheel is provided with a disk brake operated by a disk brake lever on each driving lever. 
         [0013]    Another advantage of the present invention is that the wheelchair of the present invention may be economically manufactured wherein the transmissions of both wheels are manufactured, cast, machined or otherwise formed to have identical components and a change of direction for each wheel may be provided by reversal of pawl directions. 
         [0014]    Another advantage of the present invention is that it does not contain bulky structure or components. 
         [0015]    Another advantage of the present invention is that the transmission for each wheel may be contained in a hub the size of a bicycle hub having a diameter of approximately 1 ¾″ and a length of approximately 3¾″. 
         [0016]    Briefly and basically, in accordance with the present invention, a wheelchair is provided which includes a foldable frame for supporting a seat. A first and a second wheel are attached to the frame. The first wheel includes a first transmission and the second wheel includes a second transmission. A first manually driven drive lever for driving said first wheel is provided with a pawl mechanism for engaging a ratchet surface on the first transmission. A second manually driven drive lever for driving the second wheel is provided which includes a pawl for engaging a ratchet surface on the second transmission. The first and second ratchet surfaces have a substantially radial leading and trailing edge for engaging the pawl contained on the first and second manually driven drive levers. The pawl of the second drive lever is reversed in direction as contrasted to the pawl of the first drive lever. 
         [0017]    By the ratchet surfaces having a substantially radial leading and trailing edge for engaging the pawl, it is meant and intended to cover any leading and trailing edge of a ratchet surface which may engage a pawl. In other words, neither of the leading nor trailing ratchet edge is sloped such that the pawl would slide on it, but is substantially radially formed to engage the pawl. It is understood that there may be substantial deviations from radial in terms of a surface angled from radial, such as the dovetail shape shown in  FIG. 8  such that it further enhances the ability of the pawl to engage the surface. Other deviations from radial may also be utilized and are intended to be covered by the aforesaid language, such as a concave or cupping surface formed in the leading and trailing edges of the ratchet surface. In other words, this language is intended to and does cover any ratchet surface which has a pawl engaging surface on both its leading and trailing edge so that by reversal of the pawl, the ratchet surface may be driven in the opposite direction. 
         [0018]    In accordance with a presently preferred embodiment of the present invention, the first and second transmission each have a sun gear and a planetary gear arrangement. The transmissions also each have a forward, first, second and third speed or torque power level. 
         [0019]    Further, in accordance with the present invention, the first and second drive levers are provided with a second pawl for engaging a second ratchet surface on the first and second transmissions for driving the transmissions in a reverse direction. 
         [0020]    In accordance with a presently preferred embodiment, the second ratchet surface, for the reverse direction on each transmission is provided with a substantially radial leading and trailing edge and the second pawl of the second lever is reversed in direction from the second pawl of the first lever. 
         [0021]    In accordance with a presently preferred embodiment, the transmissions are provided with a first, second and third forward speed motion which is transferred by pawl and ratchet surfaces. The ratchet surfaces have substantially radial leading and trailing edges and pawls for engaging said ratchet surfaces are reversed in direction in the first and second transmissions whereby the components of the first and second transmission may be the same except for the pawls being reversed in one transmission with respect to the other. 
         [0022]    In accordance with a presently preferred embodiment of the present invention, the wheelchair is provided with disk brake calipers mounted on the first and second drive levers for engaging a brake disk on the first and second wheels. 
         [0023]    Further, in accordance with the present invention, the wheelchair may be placed in a neutral or freewheeling condition by disengaging the first and second pawls on the first and second drive levers. 
         [0024]    Further, in accordance with a preferred embodiment of the present invention, controls for operating the wheelchair in forward or reverse direction are located on an upper portion of the first and second drive levers. 
         [0025]    Further, in accordance with a preferred embodiment of the present invention, controls for operating the wheelchair for switching between first, second or third speed are located on an upper portion of one of the first and second drive levers. 
         [0026]    Further, in accordance with a presently preferred embodiment of the present invention, the first and second transmissions are connected together by a transmission cable insuring that both transmissions are shifted to the same speed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    For the purpose of illustrating the invention, there are shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown. 
           [0028]      FIG. 1  is a view in perspective of a manually driven wheelchair in accordance with the present invention. 
           [0029]      FIG. 2  is a broken away rear view of the manually driven wheelchair in accordance with the present invention illustrating the drive levers, drive pawls and drive ratchet surfaces, shift cable connections and disk brakes as well as other structure shown therein. 
           [0030]      FIG. 3  is a cross sectional view, partially broken away, taken along line  3 - 3  of  FIG. 1  showing the internal structure of the transmission in first gear or low speed gear. 
           [0031]      FIG. 4  is a cross sectional view, partially broken away, taken along the same view as  FIG. 3  showing the internal structure of the transmission in second gear or medium speed gear. 
           [0032]      FIG. 5  is a cross sectional view, partially broken away, taken along the same view as that of  FIG. 3  showing the transmission in third gear or high speed gear. 
           [0033]      FIG. 6  is a cross sectional view, partially broken away, taken along line  6 - 6  of  FIG. 3 . 
           [0034]      FIG. 7  is an exploded cross sectional broken away view of the structure circled in  FIG. 6  showing a reversed pawl engaging a double substantially radially edged ratchet surface. 
           [0035]      FIG. 8  is a broken away cross sectional view taken along line  8 - 8  of  FIG. 3  showing a pair of pawls and substantially radially double edged ratchet surfaces. 
           [0036]      FIG. 9  is a partially broken away cross sectional view taken along  9 - 9  of  FIG. 3  showing the drive pawl for forward and reverse in connection with the double edged substantially radially directed ratchet surfaces. 
           [0037]      FIG. 10  is a view in perspective, partially broken away of the controls on the upper end of the right drive lever taken from a medial view. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    Referring now to the drawings, wherein like numerals indicate like elements, there is shown in  FIG. 1  a manually driven wheelchair  40  in accordance with the present invention. Wheelchair  40  comprises a foldable frame  42  including cross braces  44  and  46 . Frame  42  is foldable in a conventional manner of conventional wheelchairs and the present invention preserves the ability to fold and unfold the wheelchair as it is commonly done. Foldable frame  42  supports a flexible seat  48 , as well as a flexible back support  50 . Seat  48  and back support  50  may be made of any suitable flexible material such as leather, fabric, synthetic material or the like so long as it is flexible and sufficiently sturdy to support a person. 
         [0039]    Wheelchair  40  is provided with a first wheel  52  and a second wheel  54  which are utilized for propelling the wheelchair. First wheel  52  is mounted to frame  42  by mounting bracket  56  and second wheel  54  is mounted to frame  42  by mounting bracket  58  as may be seen in  FIG. 2 . Wheelchair  40  is also provided with pivotable front wheels  60  and  62 , as is conventional on wheelchairs. 
         [0040]    Each of the first and second wheels  52  and  54  is provided with a transmission mounted within its hub.  FIGS. 3 ,  4  and  5  illustrate a cross sectional view of the hub contained in right wheel  52 .  FIG. 3  is a cross sectional view of a transmission in first gear or low speed and high torque.  FIG. 4  is a cross sectional view of a transmission in second gear or medium speed and medium torque.  FIG. 5  is a cross sectional view of a transmission in third gear or high speed and low torque. 
         [0041]    Each wheel is driven by a drive lever. Wheel  52  is driven by drive lever  64  and drive wheel  54  is driven by drive lever  66  as illustrated, inter alia, in  FIGS. 1 and 2 . The lower ends of drive levers  64  and  66  are provided with a pair of drive pawls, one for forward and one for reverse, which may be selectively controlled to engage or disengage ratchet surfaces for driving in a forward direction, reverse direction or with both pawls being disengaged being in a neutral condition. Referring more particularly to  FIG. 2 , forward drive pawl  70  selectively engages double substantially radially edged ratchet surface  72  for forward driving of wheel  52 . Similarly, on the lower end of drive lever  66 , forward drive pawl  74  selectively engages forward ratchet surface  76 . As will be discussed in greater detail infra, since the left and right wheels are mirror images, rather than having to machine, cast or otherwise form different ratchet surfaces and different hubs and drive members for each wheel, in accordance with the present invention double edge ratchet surfaces are provided wherein the left and right wheel may be substantially identically manufactured with the mirror reversal of the pawl direction. 
         [0042]    The lower end of drive lever  64  is provided with a reverse drive pawl  80  which engages a reverse drive ratchet surface  82  which is also double edged. 
         [0043]    Whether the forward drive pawl engages the forward ratchet surface or the reverse drive pawl engages the reverse drive surface or whether both pawls are disengaged is controlled by a forward/reverse thumb control on the upper end of the drive lever. As illustrated in  FIG. 10  for right drive lever  64 , forward/reverse thumb control  90  is used to operate pawls  70  and  80  to either engage the forward ratchet surface  72 , the reverse ratchet surface  82  or neither ratchet surface for the neutral condition. 
         [0044]    Also illustrated in  FIGS. 2 and 10  is shift cable  92  which is controlled by thumb operated shift control  94  as shown in  FIG. 10 .  FIG. 10  is a medial view of the upper end of drive lever  64 . As will be discussed below, the operation of thumb operated shift control  94  via cable  92  operates a shift rod  23  which slidably moves within a hollow axle  11  against a spring tension in the transmission to shift gears. 
         [0045]    Referring now to  FIG. 2 , the transmission for wheel  54  is connected via cable  96  to the transmission control for the transmission of wheel  52 . In this manner, the operation of thump operated shift control  94  controls the transmission of wheel  52  via cable  92  and simultaneously controls the transmission of wheel  54  via connecting shift cable  96 . 
         [0046]    Also as illustrated in  FIGS. 1 ,  2  and  10 , wheel  52  is provided with a disk brake  100  which is controlled by a disk brake lever  98  on the upper end of drive lever  64  as shown in  FIG. 10 . Squeezing of disk brake lever  98  causes disk brake calipers  102  to engage the disk  104  of disk brake  100 . As shown in  FIG. 2 , the left wheel  54  is also provided with a disk brake  106  operated in a similar manner by a lever  108  on the upper end of drive lever  66 . 
         [0047]    Referring now to  FIG. 3 , there is shown a transmission  10  in wheel  52 . Transmission  10  may be similar to a three speed bicycle transmission, but is different, inter alia, in that there needs to be a left and a right driven transmission, means must be provided to enable the driving force to come from a lever and the transmission preferably provides a forward and reverse direction in addition to a multi-speed forward direction. In a presently preferred embodiment, transmission  10  would have a dimension of a diameter of approximately 1¾″ and a length of approximately 3¾″. The general technology of three speed bicycle transmissions is known, for example see U.S. Pat. No. 4,069,725, the teachings of which are incorporated herein by reference. 
         [0048]    To select a gear, shift rod  23  is moved in and out of hollow axle  11  of transmission  10 . Movement of shift rod  23  causes a subassembly of parts to move internally along a span of axle  11 . This subassembly consists of outer gear ring  17 , planetary gear cage  16 , planetary gears  18  and their associated pawls,  14 ,  15 ,  20  and  21  and springs.  FIG. 3  shows the transmission in first gear or low speed, high torque gear. First gear is selected by pushing shift rod  23  against internal spring  25  all the way into the body of the unit. This is done by means of cable  92 , shift cam  110  and shift rod  23 . The same shifting motion is transmitted to the transmission in wheel  54  via cable  96  and shift cam  112 . In first gear, the subassembly is all the way to the right as shown in  FIG. 3 . Third gear is selected by allowing the shift rod  23  to be pushed out or to the left of the transmission as shown in  FIG. 5  by internal spring  25 . Second gear is selected by placing the shift rod  23  at a middle point between the two extremes. 
         [0049]    In transmission  10 , all gears stay in mesh with each other at all times. The outer gear ring  17  will always turn a predetermined number of times faster than the planetary gear cage  16  and in a presently preferred embodiment it will turn 1.3 times faster than the planetary gear cage  16 , no matter what gear is selected within the transmission. The gears themselves are never shifted. Different final drive ratios are accomplished by selecting different paths of rotational torque through the transmission. Axle  11  always remains stationary as the transmission is mounted to mounting plate  56  which is mounted to frame  42 . 
         [0050]    Continuing to refer to  FIG. 3  which illustrates transmission  10  in first gear, the outer gear ring  17 /planetary gear cage  16  subassembly is shifted fully to the right. As rotational energy is applied to drive member  13  for example, by drive pawl  70  in the forward direction from drive lever  64 , outer ring drive pawls  14  engage the inner ratchet surface  17   a  of the outer gear ring  17 . The planetary gear cage drive pawls  15  slide along drive pawl disengagement ridge  17   b  and are therefore prevented from engaging in the inner ratchet surface of the planetary gear cage  16   a . In this configuration, the outer gear ring  17  will rotate at the same rate as drive member  13 . Rotational energy is transferred from outer gear ring  17  to the planetary gear cage  16  through the planetary gears  18  which are turning against stationary sun gear  9  formed in axle  11 . Because the outer gear ring  17  always rotates at a faster rate than the planetary gear cage  16 , there is a reduction in the speed of rotation in the planetary gear cage  16 . Planetary gear cage to hub drive pawl  21  engages the first/second gear ratchet surface  26  on the inner surface of hub  22 . With the outer gear ring  17 /planetary gear cage  16  subassembly in its position as illustrated in  FIG. 3 , the outer gear ring to hub drive pawls  20  slide freely along a smooth inner surface of hub  22 , next to the third gear ratchet surface  27 . As a result, hub  22  rotates at the same rate as the planetary gear cage  16 . The speed of rotation is reduced through the transmission and rotational torque is amplified. 
         [0051]    As discussed above, ratchet surfaces and transmission for the other wheel would be the same except that all of the pawls throughout would be reversed in direction. All of the ratchet surfaces are provided with pawl engagement surfaces at their leading and trailing edge and are referred to herein as radially directed leading and trailing edges. 
         [0052]    Referring now to  FIG. 4 , there is shown transmission  10  in second gear or medium speed gear or medium torque. In second gear, the outer gear ring  17 /planetary gear cage  16  subassembly is shifted halfway between its first and third gear positions. In this position, both the outer ring drive pawls  14  and the planetary cage drive pawls  15  are off the drive pawl disengagement ridge  17   b  and in contact with their respective inner ratchet surfaces  17   a  and  16   a . However, because the outer gear ring  17  always rotates faster than the planetary gear cage  16 , the outer gear ring drive pawls  14  on the drive member  13  are never able to engage the outer gear ring ratchet surface  17   a . Rotational energy is routed to the planetary gear cage  16  where it rotates about the stationary sun gear  19 . As a result, the outer gear ring  17  rotates 1.3 times faster (or some other times faster) than the planetary gear cage  16 . However, its drive pawls  20  are sliding along a smooth region of the hubs inner surface near the third gear internal ratchet surface  27  and do not apply any rotational energy to hub  22 . Therefore, planetary gear cage to hub drive pawls  21  engage the first/second gear internal ratchet surface  27 . As a result, hub  22  turns at the same rate as drive member  13 . 
         [0053]    Referring now to  FIG. 5  which shows transmission  10  in third gear, the outer gear ring  17 /planetary gear cage  16  subassembly is shifted fully to the left. In this position outer gear ring drive pawls  14  slide freely along the drive pawl disengagement ridge  17   b . The rotational energy of drive member  13  is transferred to the planetary gear cage  16  through the planetary gear cage drive pawls  15 . As the planetary gear cage  16  rotates about axle  11 , planetary gears  18  rotate about stationary sun gear  19 . They in turn transfer their rotational energy to outer gear ring  17 , which turns 1.3 times faster (or some other number) than the planetary gear cage  16 . In the third gear position, the outer ring to hub drive pawls  20  come in contact with the third gear internal ratchet surface  27  turning the hub at the same rotational rate as the outer gear ring  17 . Rotational speed is increased and torque is decreased. 
         [0054]    In summary, in first gear, rotational energy is transferred from drive member  13  to outer ring  17 , through the planetary gears  18  to the planetary gear cage  16  (at a reduced rotational rate) and to the hub  22  via hub drive pawls  21 . 
         [0055]    In second gear, rotational energy is transferred from drive member  13  to the planetary gear cage  16  and then directly to hub  22 . 
         [0056]    In third gear, rotational energy is transferred from the drive member  13 , to the planetary gear cage  16  through pawl  5 , through the planetary gears  18 , to the outer gear ring  17  (at an increased rotational rate) to the hub via pawl  20 . 
         [0057]    All internal ratchet surfaces,  16   a ,  17   a ,  26  and  27  are bi-directional so that depending upon the direction of the pawl which is inserted, the hub will turn in a desired direction. As will be discussed with respect to  FIG. 7 , regardless of the direction that the pawl  21  is inserted, it will engage with the internal ratchet surface  26 . In accordance with the present invention which requires two mirror images for the wheels to turn in the same direction, the present invention enables reduction in the cost of manufacturing since the parts are all the same for both wheels. To change a left side drive hub to a right side drive hub requires only that all the internal pawls be inserted in the opposite direction. 
         [0058]    Referring now to  FIG. 6 , there is shown a cross sectional view taken along line  6 - 6  of  FIG. 3 , which is partially broken away.  FIG. 6  shows various structure therein such as sun gear  19 , cross member  24  of shift rod  23 , planetary gears  18  as well as other structure. However,  FIG. 6  should be considered in connection with  FIG. 7  as a detailed view of hub drive pawls  21  and first/second gear internal ratchet surface  26  of hub  22 . As may be seen in  FIGS. 6 and 7 , internal ratchet surface  26  is comprised of ratchet teeth having a substantially leading and trailing edges  28  and  29 . As set forth above, the leading and trailing edges  28  and  29  are described herein for convenience as being substantially radial, but it is understood that these surfaces may be on an angle from radial as shown in  FIG. 7  wherein they may have a dovetail shape which enhances the ability of pawl  21  to engage the ratchet surface. Alternatively, as described above, the leading and trailing edges may have other shapes which enhance the ability of pawl  21  to engage the ratchet surface, such as a cup or concave shape into which the hub drive pawl would engage. It is pointed out that the leading edge becomes a trailing edge when the direction of pawl  21  is changed, such as when it is changed for the opposite wheel. As illustrated between  FIGS. 6 and 7 , the pawl in  FIG. 7  is reversed from the position shown in  FIG. 6  as it would be for the wheels on the two different sides. 
         [0059]      FIG. 8  is a partially broken away cross sectional view taken along line  8 - 8  of  FIG. 3  showing outer ring drive pawl  14 , planetary gear cage drive pawl  15  and the inner ratchet surface  16   a  of the planetary gear cage  16 . The direction of these pawls would also be reversed for the other wheel. 
         [0060]    Referring now to  FIG. 9 , there is shown a partially broken away cross sectional view taken along line  9 - 9  of  FIG. 3  showing various structure including outer ring drive pawl  14  and inner ratchet surface  17   a  of the outer gear ring  17 . The inner ratchet surface  16   a  of the planetary gear cage  16  shown in  FIG. 8  as well as the inner ratchet surface  17   a  of the outer gear ring  17  shown in  FIG. 9  are provided with substantially radially directed leading and trailing edges within the meaning as defined above. Accordingly, pawls  14  and  15  may merely be reversed for the mirror image for the other wheel. 
         [0061]      FIG. 9  also shows the drive engagement from drive lever  64  for forward drive pawl  70  and reverse drive pawl  80  which also engage forward ratchet surface  72  and reverse ratchet surface  82 , respectively, for driving in the forward and reverse directions, respectively. Again, the ratchet surfaces  72  and  82  have substantially radially directed leading and trailing edges and the mirror image for driving of the other wheel only requires that the direction of pawls  70  and  80  be reversed. 
         [0062]    The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.